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10th International INQUA Meeting on Paleoseismology, Active and Archeoseismology PATA, Hornitos, , November 2021

Short abstracts digital volume December 18, 2020

Fondecyt 1201387 PREFACE

During 2020 the humanity has been impacted by the most dramatic planetary scale health emergency in decades. Since the first announcement about the emergent pandemic (COVID-19) on December 2019 in Wuhan, China, more than 67 million people have been infected by the SARS-CoV-2 coronavirus and more than 1.5 million have been killed worldwide (Jones, N., Nature 588, 388-390, 17 December 2020). Temporary lockdowns, social distancing together with other actions to fight the pandemic strongly impacted daily routines of billions of persons, affecting the normal functioning of our societies. In addition, the average global temperature in 2020 is set to be about 1.2 ºC above the pre-industrial (1850-1900) level, according the World Meteorological Organization (2 December 2020). And the USGS reports about 128 significant earthquakes occurred worldwide (where significant is a combination of magnitude, responses and impact of the earthquakes). Together with the loss of biodiversity, famine, water scarcity -that affects billions of persons-, war and increase of socioeconomic inequalities in numerous countries in the world, this scenario challenge-us, as humans. Scientific knowledge and collaboration, humankind and Human Rights become more necessary than ever.

The 10th International INQUA meeting on Paleoseismology, Active Tectonics and Archaeoseismology, PATA, was originally programmed for November 2020 at Hornitos, in the hyperarid coastal of northern Chile, a considered as a seismic gap located along the margin of the beneath the . Because of the pandemic, we moved the date of this meeting to November 2021, with the hope that we will have the opportunity to realize fieldtrips with the aim to visit some spectacular evidences of past megathrust earthquakes and tsunamis, as well as Quaternary deformation associated to upper plate crustal faulting activity, discussing also the impact of recent and past socionatural disasters together with resilience strategies adopted by the first communities that inhabited this extreme environment.

To make this volume, we received and compiled 75 short abstracts covering the topics of active tectonics, neotectonics, tectonic geomorphology, surface deformation, landslides, surface faulting, paleoseismology, archaeoseismology, tsunami and paleotsunami records, earthquake geology and seismic hazard, as a testimony of our persistence and compromise, as worldwide community of Scientists, to contribute to making this a sustainable world.

Hope to see you in the most arid environment worldwide, the coastal Atacama Desert, in 2021.

PATA 2021 Chile Scientific Committee

December 18, 2020

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CONTENTS

PREFACE ...... 1 CONTENTS ...... 2 slip distribution along the southern 15 km of the M7.1 Ridgecrest earthquake surface rupture ...... 5 Mountain rivers reveal the earthquake hazard of geologic faults in ...... 6 Crustal Faults and Surface-Rupturing Earthquakes in The Andean Forearc: Quaternary Kinematics and Tectonic Loading of Southern Peru ...... 7 The 11/11/2019 Mw4.9 Le Teil surface rupturing earthquake, a key event for understanding the recent activity of the Cévennes fault system (S. France) ...... 8 Vertical motion rates in southern Iberia: an overview from Last Interglacial coastal units...... 9 Offshore tsunami backwash deposits – hints through biomarker analysis ...... 10 Surface rupture of the great Andean earthquake in the Central Forearc in ~AD 1400 ...... 11 Geologic evidence of past liquefactions in fine-grained lacustrine sediments (Quaternary Fucino basin, central Italy): implications for liquefaction hazard ...... 12 Dropstone Deposition Process – Insight from Comprehensive Numerical Model ...... 13 Early postglacial faulting of glaciolacustrine sediments at Round Lake, Ontario, ...... 14 Studying Ancient Tsunamis in the Geological Record in the Humid Tropics: Implications for Mexican Research ...... 15 Segmentation of long-lived strike-slip faults in intraplate : A case study of the Yangsan Fault in SE ...... 16 Variation in faulting characteristics within non-extended Stable Continental Region (SCR) crust ...... 17 Incas and Earthquakes, a peculiar and overlooked relationship. New insights from a pioneer archaeoseismological survey within the Cuzco region, Peru...... 18 Neotectonic evidence for Late Quaternary reverse faulting in the northern Chile outer forearc (22.5°S-23°S): implications for seismic hazard ...... 19 Compiling hazardous faults in : Results and lessons learned from the SARA project ...... 20 Marine terraces and knickzones as proxies for uplift transients associated to megathrust earthquakes ...... 21 New (And Quite Fast) Geologic Slip Rates Along 's Major and Oftentimes Concealed Crustal Strike- Slip Faults ...... 22 Large landslides database along the Central Western Andes (15° - 20° S): constraints on mass-movement development and implications on relief evolution ...... 23 Can the major Northern Chile Seismic Gap produce ~Mw 9.5 tsunamigenic earthquakes? Unveiling past socionatural disasters from geoarchaeological records along the hyperarid Atacama Desert at multimillennial timescales ...... 24 Offshore tsunami backwash deposits – a multi-proxy approach ...... 25 Middle-Late Pleistocene uplift of southwestern Sicily, central Mediterranean : quantitative constraints on regional and local deformation processes based on raised paleoshorelines ...... 26 Late Pleistocene and paleoseismology and deformation rates of the Pleasant Valley Fault (Nevada, USA) ...... 27 2011 Tohoku-oki and the historical Sanriki-oki tsunami - organic geochemical investigation of multiple tsunami deposits at the Aomori coast (Northern Japan) ...... 28 Multi-proxy investigation of the AD 1755 Lisbon tsunami deposits in Conil de la Frontera, Spain ...... 29

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Spatial variations in rock uplift rates in the Colca River basin inferred from landscape analysis and river terraces dating, Central Andes ...... 30 Analysis of the Damage Orientation of the 1950 Earthquake in Cusco City ...... 31 Collisional Indenter Tectonics of the Santa Ana Mountains and the Southern Los Angeles Basin, Orange County, California ...... 32 1909 Benavente Earthquake (Intensity X, Portugal): Seismic source determination through geological effects ...... 33 Paleoseismic evidence in multiple fault-branches across a transect of the Alhama de Murcia Fault (SE Spain) ...... 34 Slip rates variability along an irregular normal fault plane: Accelerated uplift accommodation during the late Quaternary, Mejillones Peninsula, northern Chile ...... 35 Structural and seismic segmentation of the Coastal Cordillera in Northern Chile: a general overview and the linking processes ...... 36 New marine terraces 10Be exposure ages in the central-eastern part of the Mejillones Peninsula, northern Chile...... 37 Geomorphological map of the Quaternary deposits of Península de Mejillones, Antofagasta (Chile)...... 38 Active tectonics of the Alps-Dinarides transition zone ...... 39 Geomorphology of the cumulative deformation since age on the Mw 4.9 Le Teil earthquake fault (South of France,11/11/19) ...... 40 Is the Billecocha fault system (Northern Ecuador) a case where strike slip faulting interacts with mountain scale gravitational deformations? Insights from morphological and paleoseismological investigations ...... 41 Characteristics of the topographical deformation in the central part of the Ulsan fault ...... 42 Earthquake clustering along strike-slip fault system A rule rather than an exception ...... 43 The Truckee fault zone, California USA: Distributed active faulting in the northern Walker Lane ...... 44 Re-assessing the probabilistic fault displacement hazard for distributed faults: it’s normal to make a fault. ... 45 Integration of faults, earthquakes and geodetic data for estimating PSHA: the Italian model...... 46 Inferring seismic hazards from a new 1:25,000 scale map of active and potentially-active continental faults in Chile ...... 47 Rupture History of the Himalayan Frontal Thrust in Central Nepal ...... 48 Recording the giant 1877 CE tsunamigenic earthquake and its predecessors from submarine laminated sediments off Northern Chile (19°35’S) ...... 49 Outreach on Earthquake Geology as a tool to increase social seismic awareness ...... 50 Surface rupturing earthquake in the Lower Rhine Grabens: results from paleoseismological trenching – “one shot faults”? ...... 51 Quaternary deformation along the Western Andean Front (WAF) between 35° and 37° S, Chile: insights from morphometric analysis ...... 52 Speleoseismology as a tool to validate and constrain seismic hazard models: examples from Central and Southern Apennines in Italy...... 53 Morpho structural and Paleo-seismological analysis of the Pachatusan Fault System –Cusco, Peru ...... 54 Slow-slip active faults in tropical areas: the case of the Opak Fault System (Central Java, Indonesia) ...... 55 Radon (222Rn) soil exhalation of the Alhama de Murcia fault and earthquakes...... 56 Speleoseismology at Los Casares Cave (central Sapin): evidence of a paleoearthquake? ...... 57 Pleistocene earthquakes in the Southern Peribalticum area - the GREBAL project summary ...... 58

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Evidence of Holocene Subduction Earthquakes on the Central Hikurangi Subduction Margin ...... 59 Sand deposits reveal great earthquakes and tsunamis at Mexican Pacific Coast ...... 60 Surface rupturing earthquake in the Upper Rhine Grabens: results from paleoseismological trenching ...... 61 Active faults or weakness zones in the northern Chile forearc? Understanding the competition between subduction earthquake cycle and upper plate fault reactivation in subduction zones ...... 62 Rupture Complexity in Large Strike-Slip Earthquakes: Rule or Exception? ...... 63 Paleoseismic Studies in Cusco: Evidence of paleo-earthquakes in the surface rupture zone of the 1986 earthquake ...... 64 Seismic Potential of Crustal Faults in the Chilean Andes ...... 65 Locating Active (Holocene) Faults in the City of Beverly Hills, California (USA) ...... 66 Archeoseismological analysis of the late 4th century tsunami event devastating the Roman City of Baelo Claudia ( Arc, South Spain)...... 67 The evolution of slopes in a seismically active carbonate terrain by normal faulting and generations of landslides, , Israel ...... 68 Stress field changes in Central since Late to date as determined from volcanic rocks and extensometric measurements in the Bohemian Massif, ...... 69 Fault reactivation due to Ice Loading (Bohemian Massif, Central Europe) ...... 70 Neotectonic deformations in a cave: constraints from Th/U dating of damaged speleothems (Demänová cave system, Low Tatra Mts, Western Carpathians) ...... 71 Coseismic paleo-displacements along the Mt. Vettore bedrock fault scarp revealed by high resolution topographic survey (central Italy, 2016 earthquake) ...... 72 Offshore tsunami backwash deposits - How to interpret palynological and micropalaeontological records? .. 73 Palaeostress inversion from post-glacial scarps on the Hellenic Subduction Forearc ...... 74 IPOC Creep as a natural lab: Deciphering fault slip behavior from fault gouge structure and composition and high rate instrumental monitoring with the IPOC Creepmeter array ...... 75 Glacial Quaternary geology of the Patagonian Andes across the Coyhaique-Puerto Aysén transect constrains neotectonics and paleoseismological observations along the Liquiñe-Ofqui Fault Zone ...... 76 Exploiting local geological data for fault-based seismic risk: a Fault2SHA experience...... 77 The Truckee River Terraces of Reno ...... 78 Discussion on the possibility of glacial earthquakes during mid/late MIS 2 in the southern Baltic onshore settings ...... 79

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Fault slip distribution along the southern 15 km of the M7.1 Ridgecrest earthquake surface rupture

Sinan O. Akciz (1), Salena Padilla (1), Alex Hatem (2), James F. Dolan (2)

(1) CSU Fullerton, Geological Sciences, Fullerton, CA, (2) University of Southern California, Earth Sciences, CA, United States

Abstract: The Mw7.1 Ridgecrest earthquake of 5 July 2019 occurred in the transition area between the Eastern California Shear Zone in the and the Walker Lane to the north, which accommodates roughly 10 mm/yr of the motion between the North American and Pacific plates. We mapped the southernmost 15 km of the rupture, which cut across Pleistocene lacustrine and alluvial deposits. We followed the main rupture southeastwards from Highway 178, making field observations of fault orientations, slip sense, fault zone width, and displacement measurements. Eighty-two offset measurements were made along the main (eastern) and central strands of the ruptured fault zone, including measurements made on cracks. The summary of our displacement data are: (1) a minimum of 70 cm of right-lateral slip occurred along the main fault rupture, but the displacement rapidly decreased to <2cm within one km of Highway 178, and continued beyond that to the south as discontinuous fractures; (2) at this one-km mark, rupture steps left across a 500-m-wide zone of distributed fracturing, before consolidating along a dominantly left-stepping zone of en-echelon faults and fault splays, with a typical width of ~ 20-50 m; (3) south of the stepover area, surface fracturing with measurable offsets occurred along three sub-parallel faults. The eastern strand exhibited right-lateral displacements of 70 – 120 cm, the central strand accommodated a maximum of ~30 cm of dextral slip, and the western strand is mainly a zone of distributed fracturing with <5 cm displacements; (4) Dislodged boulders and cobbles observed at the fault endpoints within this restraining stepover region indicate high accelerations that locally exceeded Earth’s gravity; (5) nearly 100 cm right-lateral slip along the eastern strand extended to within 500 m of the southern end of the rupture trace, which ended ~5 km north of the Garlock fault.

Keywords: Fault slip distribution, Ridgecrest earthquake

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Mountain rivers reveal the earthquake hazard of geologic faults in Silicon Valley

F. Aron (1, 2), S. Johnstone (2,3), A. Mavrommatis (4†), R. Sare (2), F. Maerten (5), J. Loveless (6), C. W. Baden (2), G. E. Hilley (2)

(1) Research Center for Integrated Disaster Risk Management (CIGIDEN) & Departamento de Ingeniería Estructural y Geotécnica, Pontificia Universidad Católica de Chile, Macul, 7820436, Chile. (2) Department of Geological Sciences, Stanford University, Stanford, CA 94305. (3) Geosciences and Environmental Change Science Center, United States Geological Survey, Denver, CO 80225-0585. (4) Department of Geophysics, Stanford University, Stanford, CA 94305. (5) YouWol, 455, Avenue Alfred Sauvy, Le Lancaster, 34470 Perols, France. (6) Department of Geoscience, Smith College, Northampton, MA 01063.

Abstract: The 1989 Mw=6.9 Loma Prieta earthquake resulted in tens of lives lost and cost California almost 3% of its GDP. Despite widespread damage, the earthquake did not clearly rupture the surface, which poses a challenge to identifying and characterizing these hidden hazards. Here, we show that these hazards can be illuminated by inverting earth's river topographic structure for fault slip- and moment accrual-rates – two fundamental components in earthquake hazard assessments – by combining a geomorphic model of channel incision with a mechanical model of slip along crustal, relief-generating faults. We applied this technique to a set of thrust faults bounding the mountains along the western side of Silicon Valley in the Area and discovered that: (i) a Mw=6.9 earthquake could occur on these faults over the next 100-250 years; if they were to rupture today the quake could reach up to Mw=6.5-6.7, and (ii) this method may be deployed broadly to evaluate seismic hazard in developing regions with limited geological and geophysical information.

Keywords: Mountain rivers, earthquake hazard, Silicon Valley

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Crustal Faults and Surface-Rupturing Earthquakes in The Andean Forearc: Quaternary Kinematics and Tectonic Loading of Southern Peru

Audin, L. (1), Benavente, C. (2), Rosell, L. (2), García, B. (2), Zerathe, S. (1), Delgado, F., Aguirre, E. (2), Robert, X. (1), Saillard, M. (3), Hall, S. (4), Costa, C. (5).

(1) ISTerre, Université Grenoble Alpes – IRD, France (2) Instituto Geológico, Minero y Metalúrgico INGEMMET, San Borja, Perú (3) Université Côte d'Azur, IRD, CNRS, Observatoire de la Côte d'Azur, Géoazur, Valbonne, France (4) College of the Atlantic, Maine, USA (5) Departamento de Geología - Universidad Nacional de San Luis - Argentina

Abstract: As recurrence intervals of crustal surface-rupturing earthquakes reach thousands to tens of thousands of years in the Andes, slip rates on individual faults are barely measurable by instrumental networks. Consequently, satellite geodesy or even historical seismic catalogues do not reflect Quaternary nor Holocene long-term deformation patterns. Nonetheless, an increasing amount of geomorphic data and paleoseismic records shows that the continental Andes also accumulates strain with respect to megathrust interface. In the forearc and Western Cordillera of the Central Andes, the tectonic loading is shared by a complex system of interacting faults spread across the landscape, which are major but often seismically quiet fault zones. This work explores some of the key places previously studied in Southern Peru, taking them all together in an attempt to reach a broader understanding of distributed crustal deformation. Field mapping complemented with topographic data, air photos and satellite images analysis allow precise determination of piercing points across the Atacama landscape that are used to measure fault offsets and to map the tectonic markers. Geochronological dating (TCN, OSL, C14) provide constraints to determine long-term slip rates. On a 10-100 ka time-scale, the displacement rates range from 5 mm/yr to 0.1 mm/yr. Those rates are about 5 mm/yr faster than short-term geodetic null estimates for this part of the Andes. This result also highlights a need for new constraints on hazard assessment regarding the seismic cycle linked to the subduction processes and interseismic coupling. Our study shows that now active faults are identified, we need more sites along the Western Cordillera in Peru and Chile need to be targeted to better constrain the slip rates over different timescales, both to create a more complete picture of distributed deformation throughout the forearc region (spatial) or to span multiple timescales.

Keywords: Quaternary crustal faults, Andean forearc, Peru

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

The 11/11/2019 Mw4.9 Le Teil surface rupturing earthquake, a key event for understanding the recent activity of the Cévennes fault system (S. France)

Stéphane Baize (1), Jean-François Ritz (2), Estelle Hannouz (3), Magali Riesner (4), Laurence Audin (3), Pierre Arroucau (5), Laurent Bollinger (4), Matthieu Ferry (2), Hervé Jomard (1), Christophe Larroque (6), Kevin Manchuel (5), Magali Rizza (7), Christian Sue (3)

(1) Institut de Radioprotection et Sûreté Nucléaire, Fontenay-aux-Roses, France (2) Géosciences Montpellier, France (3) IsTerre, Université de Grenoble – Alpes, France (4) Commissariat à l’Energie Atomique, France (5) Electricité de France, Aix-en-Provence, France (6) Géoazur, Université de Nice – Sophia-Antipolis, France (7) CEREGE, Aix-en-Provence, France

Abstract: On November 11, 2019, a very shallow and moderate Mw4.9 earthquake occurred in southern France, causing significant damages and unexpected surface rupture. This earthquake that surprised inhabitants, authorities and media appears as an infrequent event in this slowly deforming region. The earthquake rupture occurred on a 5 km-long fault section along the La Rouvière fault, (LRF) belonging to the Cévennes fault system (CFS). This major inherited structure acted as a normal fault during the Oligocene extensional episode (20-30 Ma ago), whereas the 2019 earthquake inverted the sense of motion with a reverse focal mechanism confirmed by field observations and geodetic measurements (Ritz et al., 2020). InSAR data show that evidences of discrete surface faulting, warping and fissuring occurred in a wide band of tens to hundreds of meters, which follows the geological trace of the LRF. Maximum vertical displacement over the whole deformation band is ~25 cm, and localized vertical surface displacement locally reaches ~15 cm. The LRF, previously not known as an active fault, is now under careful investigation, as well as the other faults of the CFS. In the framework of a national effort (so-called “FACT axis” within the French RESIF consortium, a national research infrastructure: www.resif.fr/en/), we started to investigate the recent tectonics of the CFS, including mapping, geomorphological analysis and paleoseismological research. To date, one year after the earthquake, we could gather evidences of pre-2019 Quaternary deformation in the first paleoseismological trenches along the LRF. The aim of this study is to check the occurrence of previous surface-rupturing events and to determine the slip rates along faults, which are key parameters to evaluate the regional ground motion and surface rupturing hazards. These data will also provide constraints for better understanding the regional geodynamics of the studied region.

Ritz et al. (2020). https://www.nature.com/articles/s43247-020-0012-z

Keywords: Moderate earthquake surface rupture, Paleoseismology, France, Stable Continental Region

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Vertical motion rates in southern Iberia: an overview from Last Interglacial coastal units.

T. Bardají (1), J.L. Goy (2), C. Zazo (3), C.J. Dabrio (4), D. Moura (5), T. Boski (5), E. Roquero (6), P.G. Silva (2), A. Martínez-Graña (2), J. Lario (7)

(1) Dpto. Geología, Geografía y Medio Ambiente; Universidad de Alcalá. 28805-Alcalá de Henares. [email protected] (2) Dpto. Geología; Universidad de Salamanca. 37008-Salamanca. [email protected]; [email protected] (3) Dpto. Geología; Museo Nal. CC. Naturales; CSIC. 28006-Madrid. [email protected] (4) Dpto. Estratigrafía; Universidad Complutense de Madrid. 28040-Madrid. [email protected] (5) CIMA; Universidad do Algarve. Portugal. [email protected]; [email protected] (6) Dpto. Edafología; ETSI Agrónomos; Universidad Politécnica de Madrid; 28040-Madrid. [email protected] (7) Dpto. CC. Analíticas, Fac. Ciencias; UNED. 28040-Madrid. [email protected]

Abstract: Low to moderate tectonic rates since the Pliocene have been described in Southern Iberia, currently subjected to the compressive stress produced by the convergence between the Eurasian and Nubian plates. This complex active plate boundary is characterized, between Azores and Tunisia (Bufforn & Udías, 2010), is characterized by being partially coincident with coastal settings. Southern Iberia is a key site to understand the local and regional responses to this shortening by analysing an accurate reference level such as the Last Interglacial sea level. To accomplish this goal several assumptions were made: similar behaviour of sea level in the open oceanic mesotidal Atlantic coast and in the closed microtidal Mediterranean coast; the difference in sea level between Mediterranean and Atlantic coasts has remained unchanged since the last Interglacial (approx. 20cm at present, Ihde & Augath, 2000); age of MIS 5e peak at 130ka and sea level at 6m a.p.s.l. (Capron et al., 2019). Taking these assumptions into account, a maximum uplift of 0,11 - 0,12 mm/yr has been calculated for the Portuguese southern margin (Algarve) and Gibraltar Strait, and minimum subsiding rates of 0,20 – 0,002 mm/yr in Alicante – Murcia (Pérez-Peña et al., 2020) and Alentejo (Goy et al., 2019). GPS data (Stich et al., 2006; Koulali et al., 2011; Cabral et al., 2017) reveal different present-day motions along this boundary, with tectonic scenarios varying from left lateral shear in the Eastern Betics (Montenat et al., 1987, Silva et al., 1993) to right lateral shear in Southwestern Portugal (Cabral et al., 2017). The overall NWN- ESE transpressive regime of Southern Iberia can account for the relatively moderate uplift and subsidence rates recorded since the Last Interglacial (Zazo et al., 1998). The objective of this contribution is to compare the vertical motion trends calculated from the present altitude of Last Interglacial units, with the different tectonic scenarios and local changes along this complex boundary.

Keywords: Vertical motion; MIS5; Southern Iberia

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Offshore tsunami backwash deposits – hints through biomarker analysis

Piero Bellanova (1,2), Mike Frenken (1,2), Jan Schwarzbauer (2), Lisa Feist (1), Pedro Costa (3,4), Juan I. Santisteban (5), Helmut Brückner (6), Klaus Reicherter (1) and the M152 scientific Team

(1) Neotectonics and Natural Hazards Group, RWTH Aachen University, Germany (2) Laboratory for Organic-Geochemical Analysis, Institute of Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University, Germany (3) Instituto D. Luiz, Faculdade de Ciências, Universidade de Lisboa, Portugal (4) Earth Sciences Department, Faculty of Sciences and Technologies, University of Coimbra, Portugal (5) Department of Geodynamics, Stratigraphy and Paleontology, Fac. Geological Sciences, Complutense University of Madrid, Spain (6) Institute of Geography, Department of Geosciences, University of Cologne, Germany

Abstract: Little is known about offshore tsunami backwash deposits. Their sedimentary processes, impact on benthic life and preservation potential are as yet unexplored. Few offshore sedimentary archives have been studied for tsunami research. One of these is the shelf record of southwestern Iberia, where the M152 RV Meteor expedition sampled a coast-perpendicular transect off the Algarve coast (water depths: 65-114 m). When tracing the offshore sedimentary footprint of the AD 1755 Lisbon tsunami backwash, a predecessor tsunami layer has been identified. While records of the AD 1755 tsunami and a potential predecessor are well documented onshore, the offshore record of the sedimentology and dynamics of the backwash are as yet unexplored. At least two tsunami deposits (AD 1755 and ca. 3700 cal. BP) were detected in vibracores obtained from the Algarve shelf seafloor. A multi-proxy approach allowed to identify and differentiate these event deposits from the background sedimentation. Organic-geochemical biomarker proxies, such as n-alkanes, polycyclic aromatic hydrocarbons, terpenes and n-aldehydes, were used for a clear identification of the terrestrial-influenced backwash. Further, the organic-geochemical signature of the onshore deposits of the AD 1755 tsunami from the famous Boca do Rio site were compared with the proxies detected in the offshore backwash deposits. In the latter, the biomarker assemblage is less distinctive, but still shows a significant discrimination from the surrounding sediments. Therefore, the Algarve shelf is a reliable archive for Holocene tsunami imprints. It may extend the onshore record with its much lesser preservation potential due to subaerial erosion and present-day coastal morphology being established only since the last four millennia. Multi-proxy approaches, including organic-geochemical parameters, are a vital tool to (i) identify tsunami backwash deposits; (ii) help in calculating recurrence intervals; and (iii) estimate the hazard potential for the related coastal area.

Keywords: AD 1755 Lisbon tsunami, tsunami backwash, offshore tsunami, organic geochemistry

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Surface rupture of the great Andean earthquake in the Central Andes Forearc in ~AD 1400

C. Benavente (1)*, L. Rosell (1), E. Aguirre (1), X. Robert (2), B. García (1), F. Delgado, S. Zerathe, L. Audin (2), A. Palomino

(1) Instituto Geológico, Minero y Metalúrgico INGEMMET, San Borja, Perú (2) Université Grenoble Alpes, CNRS, IRD, ISTerre, 38000 Grenoble, France (3) Especialidad Ingeniería Geológica, Facultad de Ciencias e Ingeniería. Pontificia Universidad Católica del Perú, San Miguel, Lima 15088, Perú. *[email protected]

Abstract: Seismic hazard in Peru is often considered to be dominated by earthquakes on the subduction interface. In the Central Andes Forearc, the size of the sources and the recurrence time of strong crustal earthquakes are unknown, because geomorphologic and active fault mapping remains scarce. Here, we use high-resolution DEMs, geomorphic features of surface ruptures, paleo-seismological evidences on alluvial terraces and trench walls, and 14C dating constraints to show a primary >100 km surface rupture along the Incapuquio Fault System (IFS). This is considered as the most important frontal thrust in the western margin of the Central Andes. The values of the net slip vary between 1.2±0.14 to 1.6±0.18 m. Modeling of calibrated 14C evidences that the last surface rupture occurred in the early 15th century (~AD 1400). According to the fault- rupture parameters, we estimate that the earthquake was Mw>7.2. No instrumental large intraplate earthquake has been recorded in the Central Andean Forearc yet and paleoseismic studies are the only way to address the hazard evaluation. Though, this area has been occupied by human civilizations since at least 4 ky but the historical catalogue of earthquakes in Peru is limited to the last 500 yrs. Consequently, the impact on any ancient civilization is not known. According to recent archaeological research, the Chiribaya civilization inhabited southern Peru until ~AD 1400, contrary to the idea that attributes the end of civilization to “mega-Niño” Miraflores climatic catastrophe (AD 1330). Therefore, we propose that the end of the Chiribaya civilization is associated with the reactivation of the Incapuquio fault system.

Keywords: Surface rupture, Andean earthquake, Central Andes forearc

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Geologic evidence of past liquefactions in fine-grained lacustrine sediments (Quaternary Fucino basin, central Italy): implications for liquefaction hazard

Paolo Boncio (1,2), Sara Amoroso (1,3), Fabrizio Galadini (3), Antonio Galderisi (1,4), Gianluca Iezzi (1,3)

(1) Università “G. D’Annunzio” Chieti-Pescara, Chieti, Italy (2) CRUST - Centro inteRUniversitario per l'analisi SismoTettonica tridimensionale con applicazioni territoriali, Chieti, Italy (3) Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy (4) Istituto di Geologia Ambientale e Geoingegneria, CNR, Rome, Italy

Abstract: Liquefaction of fine-grained sediments (silt/clay-size particles) is a topic of interest for earthquake geology and local seismic hazard studies. Actually, the believing that significant liquefaction hazard is associated primarily to the presence of loose sands is still diffuse among geologists and engineers. We present the results of a study carried out in the Fucino lacustrine basin in central Italy, where there is evidence of earthquake-induced past liquefactions within a fine-grained stratigraphic succession of Quaternary age. We studied in detail clastic dykes exposed on the walls of an artificial channel. The dykes are filled by fine- grained sediments. A multidisciplinary analysis (earthquake geology, geognostic drilling, geotechnics, Vs profiling, X-Ray Powder Diffraction mineralogical analysis, XRPD) allowed us to characterize the stratigraphic succession beneath the dykes. The stratigraphic succession down to 20 m depth is formed by prevailing silt or silt-clay mixtures ~170-180 kyrs-old. Geologic observations suggest that the dykes are filled by silt liquefied and transported upwards by hydraulic forces of short duration, as for earthquake-induced liquefaction. Geotechnical simplified methods allowed us to estimate a high liquefaction hazard. Correlations of XRPD mineralogy of samples from dykes with those from drilling cores allowed us to identify the most likely source layer filling the dykes, corresponding to a silt layer at 7-8 m depths. This layer and the dykes lack illite and montmorillonite clay particles. These results contribute to improve studies of liquefactions in sediments that differ from typical liquefiable loose sands. Implications for the assessment of liquefaction hazard in late Quaternary fine-grained lacustrine sediments are discussed.

Keywords: Liquefaction, fine-grained sediments, lacustrine sediments, clastic dykes, Fucino basin

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Dropstone Deposition Process – Insight from Comprehensive Numerical Model

Małgorzata Bronikowska (1), Małgorzata Pisarska-Jamroży (1), A.J. (Tom) van Loon (2)

(1) Institute of Geology, Adam Mickiewicz University, B. Krygowskiego 12, 61-680 Poznań, Poland. e-mail: [email protected]; [email protected] (2) College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, Shandong, China

Abstract: Due to gradual melting of free floating and drifting at the lake surface ice, clasts (dropstones) of all sizes are set free and eventually settle through the water column. Although the dropstones in glaciolimic and marine sediments have frequently been described by many authors, no previous studies based on numerical modelling has been addressed the dropstones deposition process in general. Here we present results of our comprehensive numerical model devoted to the relationship between dropstone size, water depth and resulting SSDS. In aim to model the dropstone deposition process, two separate but complementary numerical methods has to be combine. First of them addresses impact velocity calculations, while the second one allow the investigation on the response of bottom sediments on pressure caused by impacting clast. The presented comprehensive model allows the reconstruction of the depositional process of dropstones (which have been modelled in the present study to be spherical and homogeneous). The deformations caused by the impacting dropstone strongly depend on its diameter; the exact measurements of these soft-sediment deformation structures can also provide information about the impact scenario. There is a water depth that limits further increase of the settling velocity of a dropstone (and thus of its impact velocity); the velocity becomes constant after reaching this depth, which depends only on the dropstone size. For dropstones in basins that are deeper than the velocity-limiting depth, the reconstruction of the water depth is no longer possible.

Keywords: Dropstone deposition, numerical model

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Early postglacial faulting of glaciolacustrine sediments at Round Lake, Ontario, Canada

Brooks, Gregory R. (1), Pugin, André J.-M. (2)

(1) Geological Survey of Canada, Natural Resources Canada, 601 Booth Street, Ottawa, Ontario, Canada, K1A0E8, Email [email protected] (2) Geological Survey of Canada, Natural Resources Canada, 601 Booth Street, Ottawa, Ontario, Canada, K1A0E8, Email [email protected]

Abstract: Round Lake, ~12 km2 and up to 30 m deep, is located in an intracratonic setting on the , northeastern Ontario, Canada, about 180 km northwest of the Western Quebec Seismic Zone. Within a ~0.5 by 1.8 km area of the lake sub-bottom, acoustic and hammer seismic surveys revealed multiple, low- angled, normal faults that were identified previously as candidates for early postglacial, glacially-induced faulting. As exemplified by three scarps, the faults have apparent throws of about 3 to 6 m and form obvious steps within the glaciolacustrine deposits to the depth of penetration in the acoustic profiles. Unfaulted glaciolacustrine deposits are draped across the faulted sediments, indicating that the faulting occurred in the early postglacial period between 9.8-8.47 ka cal BP, when a large glacial lake inundated the regional landscape. Hammer seismic profiles display signal penetration into the underlying glacial deposits, and reveal that the faulting at many of the scarps is confined to the glaciolacustrine deposits. This characteristic is consistent with the fault surfaces representing the headscarps of shallow mass movements within the glaciolacustrine deposits. Several of the faults are deeper-seated, and may originate below the glaciolacustrine facies, as indicated by i) the apparent extension of the fault planes to the surface of underlying glacial deposits, ii) the identical sub-unit architecture in the head- and footwalls, and iii) the lack of fracturing, back rotation, and disruption to the headwall sub-units, which would be indicative of displacement by a mass movement(s). Lack of penetration of the acoustic or hammer seismic signals to bedrock does not allow determining whether this deeper-seated faulting is associated with bedrock faulting.

Keywords: Early postglacial faulting, glaciolacustrine deposits, shallow geophysics,

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Studying Ancient Tsunamis in the Geological Record in the Humid Tropics: Implications for Mexican Research

Rocío Castillo-Aja (1), María-Teresa Ramírez-Herrera (2)

(1) Departamento de Geografía y Ord. Territorial, Universidad de Guadalajara, Guadalajara, Jalisco (México). [email protected] (2) Laboratorio de Tsunamis y Paleosismología, Instituto de Geografía, Universidad Nacional Autónoma de México, Ciudad de México. [email protected]

Abstract: Tsunami deposits, preserved in the geological record, are a key tool in the reconstruction of tsunami chronology, and in the assessment of tsunami hazard along coastal areas of tsunamigenic zones. The Indian Tsunami (2004) boosted research efforts in tsunami deposits studies in a humid tropical environment, however the study of this type of deposits in the humid tropics have been reported as challenging. Tsunami deposits studies have been developed mainly where modern analogues have occurred, nevertheless, many areas, near subduction zones in humid tropical environments, remain little explored. Here, we discuss the state of knowledge of deposits of ancient tsunamis in the humid tropics; including both historical and prehistorical events, summarize tools used and problems faced in identifying and dating them. Some of the challenges faced in the identification of deposits of ancient tsunami in humid tropics are tropical storms, which are still not completely solved; and, although historic data are helpful guides identifying ancient tsunamis, for some regions the improvement of chronologies remain as a pending task. Nevertheless, results reported in literature show that a multi-proxy approach and the formation of multidisciplinary teams has yielded encouraging results towards identifying these deposits in the humid tropics. Finally, we discuss the experience in studies of ancient tsunamis deposits in the Mexican Pacific Coast, which brings together two challenges, a humid tropical environment plus the lack of a big modern analogue, aiming to contribute with a Mexican tsunamis research agenda.

Keywords: Ancient tsunamis, humid tropics,

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Segmentation of long-lived strike-slip faults in intraplate regions: A case study of the Yangsan Fault in SE Korea

Jin-Hyuck Choi (1)

(1) Center for Active Tectocnis, Geology Division. Korea Institute of Geoscience and Mineral Resources, Korea. [email protected]

Abstract: Fault systems associated with destructive earthquakes consist of a number of individual fault segments. Earthquake recurrent patterns are often independent on each fault segments, and neighboring fault segments are often sequentially ruptured by a single seismic event. Hence, segment geometry plays a key role in evaluating earthquake cycle model in a given fault system. Also segment geometry of fault systems is one of the essential parameters to assess earthquake hazards. A detail map of coseismic surface ruptures associated with recent earthquakes, including along-rupture variations in geometry and offset, provide an opportunity to examine segmentation of the faults. In some cases of no recent surface-faulting events, historical and paleoseismological data could be used as an indicator of the fault segmentation. Shortly, fault segmentation could be identified by investigations of surface ruptures associated with historical earthquakes. In intraplate regions, however, major fault systems in general were not ruptured during historical period due to long (> thousands of years) recurrence time. Paleoseismological data is also extremely rare to test segment geometry. Here, I investigate segment geometry of the Yangsan Fault, which is one of the major, ~ 180 km long, active strike-slip faults in Korean Peninsula. There are limited paleoseismic data and no surface-faulting by instrumental seismic events along the fault. Tools for the segmentation of the fault are distributions of micro seismicity, fault-related geomorphic features, and geometric discontinuities along the fault valley. Also we consider inherited geology of surrounding area of the fault defined by field observations and geophysical surveys. The results indicate that the Yangsan Fault could be divided into three major segments with a total of more than fifteen sub-segments.

Keywords: Active Fault, Intraplate Strike-slip Fault, Segment Geometry

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Variation in faulting characteristics within non-extended Stable Continental Region (SCR) crust

Dan Clark (1)

(1) Geoscience , GPO Box 378, Canberra, ACT 2601, Australia, Email: [email protected]

Abstract: Broad agreement exists that SCR crust is not homogeneous with respect to seismogenic potential. The majority of historical moment release in SCR settings is preferentially located in failed rifts of to age, and associated with pronounced lateral gradients in lithospheric thickness such as at the boundaries of cratons. While accounting for less than 10% of historical global SCR moment release, non- extended SCR crust accounts for more than two-thirds of the surface-deforming earthquakes documented, and is locally associated with a rich paleoseismic record. The Australian non-extended SCR can be divided into Precambrian and Phanerozoic components based on differences in seismogenic potential implied by the character of neotectonic features. Herein we present results from two paleo-seismic studies that are illustrative of endmember behaviours. The 2018 Lake Muir earthquake sequence culminated in a MW 5.3 event that produced a 3 km-long and up to 0.4-0.6 m high surface rupture. It is representative of a class of ruptures in the Precambrian non-extended SCR of Australia where the scarps are isolated from each other and there is little or no landscape evidence for the recurrence of surface-deforming earthquakes, or of the construction of regional tectonic relief. In contrast, the ~75 km-long Lake George Fault scarp, in Phanerozoic eastern Australia, is associated with ~250 m of relief- building in the last ca. 4 Myr. The fault is part of a connected network of faults that straddle the crest of the continental divide in the southeast highlands. Episodes of activity on the fault involving tens of metres of uplift are separated by much longer periods (≤10 times) of quiescence. While individual seismic events have not been resolved, standard relations between rupture length and single event displacement suggest that the record may relate to one hundred seismic cycles or more.

Keywords: Stable continental region, intraplate seismicity, episodic rupture, one-off rupture, seismic hazard, paleoseismology

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Incas and Earthquakes, a peculiar and overlooked relationship. New insights from a pioneer archaeoseismological survey within the Cuzco region, Peru.

A. Combey (1), L. Audin (2), C. Benavente Escóbar (3), M.A. Rodríguez-Pascua (4), J. Bastante (5)

(1) ISTerre, Université Grenoble Alpes – PhD CDP Risk (2) ISTerre, Université Grenoble Alpes – IRD (3) Geología Ambiental, Instituto Geológico Minero y Metalúrgico, Lima, Peru (4) Instituto Geológico y Minero de España, Madrid, Spain (5) Director of the archaeological park of Machu Picchu, Cuzco, Peru

Abstract: Far away from the Pacific margin and its repeated and devastating megathrust earthquakes (Lima, 1746; Arica, 1868), the Cuzco region, heartland of the Incas, is nevertheless a seismic prone region characterized by a high vulnerability. The large tectonic structure that crosses the area, the Cuzco Vilcanota Fault Complex, triggered indeed several destructive events since the Spanish Conquest (1650, 1950, 1986, 2014). Worldwide known for their megalithic constructions, the Incas are often considered as the inventors of a singular seismic-resistant architecture. However, did they experience as well large ground shaking episodes? In the absence of pre-Hispanic intelligible written sources, the dense human occupation of the Cuzco area over the last two millennia makes thus archaeological remains a valuable marker for paleo-seismicity characterization. In order to improve the seismic catalogue and extend our knowledge on the Inca seismic risk management we carried out the first detailed archaeoseismological survey in Peru. Based on a field-tested and quantitative methodology, our approach led to the identification and registration of a large number of Earthquake Archaeological Effects (EAEs) on monumental pre-Columbian sites of the Cuzco and Sacred Valley. Combined with other evidences of past seismic activity like fault trenching, lake coring and ethnohistorical sources, we aim to date prehistorical earthquakes and assess their induced social effects. Our first results suggest the occurrence of, at least, one important seismic event during the Late Horizon (1400- 1533 AD) and argue for a reappraisal of previous archaeological interpretations. Shedding a new light on the complex relation between Incas and earthquakes, our investigations are likely to have implications in the current hazard assessment and might be crucial in inventing Andean societies more resilient.

Keywords: Archaeoseismology, megalithic architecture, risk perception, Inca, Peru

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Neotectonic evidence for Late Quaternary reverse faulting in the northern Chile outer forearc (22.5°S-23°S): implications for seismic hazard

Cortés-Aranda, J. (1, 2); González, R.; Fernández, V.; Astudillo, L.; Miller, M.; Molina, D.; Oviedo, A.; González, J.

(1) Departamento de Ciencias de la Tierra, Universidad de Concepción, Concepción, Chile. (2) Millennium Nucleus The Seismic Cycle Along Subduction Zones, Valdivia, Chile

Abstract: In the northern Chile outer forearc (between 19°S and 23°S), extension is the dominant deformation style conducted by crustal faults during the -Quaternary time span. Most of this extension has been produced by normal faulting along submeridian branches of the System (AFS). During the Late Quaternary, several of these faults have built conspicuous metric-scale normal faulting scarps in alluvial deposits; the construction of these scarps has been related, in some cases, to M~7 normal faulting paleoearthquakes. On the contrary, shortening during this time span has been only locally reported. Until now, no metric-scale reverse faulting scarps have been documented along submeridian strands of the AFS. In this study, we present novel evidence for localized Late Quaternary shortening led by three NNE and NNW trending faults in the outer forearc between 22.5°S and 23°S: the El Toro, Buey Muerto and Sierra Valenzuela faults. The most recent deformation increments along these faults are compatible with reverse kinematics and produced remarkable scarps in basement rocks, pre-Quaternary and/or Quaternary alluvial deposits. Based on their characteristics, we interpret that these scarps are due to single reverse faulting paleoearthquakes. Considering the maximum scarp height as a proxy for the coseismic slip, and fault length as a proxy for surface rupture length, we have estimated magnitudes between 6.2 and 6.9 for the causative rupture events. Furthermore, we calculate the horizontal displacement field at 5 km depth induced by the 1995 Antofagasta Earthquake, the 2007 Tocopilla Earthquake, and a synthetic deep earthquake in the 1877 Iquique Segment, to discuss how megathrust ruptures may explain the observed reverse faulting in the study area; the same is performed for the interseismic locking distribution for the megathrust in the 1877 Iquique Segment. Our results suggest that these faults may experience reverse slip during both stages of the subduction cycle. Finally, we reinforce the need for addressing the earthquake potential of the studied faults, and others similar, to acquire a more complete assessment of the seismic hazard in the northern Chile outer forearc.

Keywords: Northern Chile; Late Quaternary fault scarps; reverse faulting paleoearthquakes; subduction cycle.

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Compiling hazardous faults in South America: Results and lessons learned from the SARA project

Carlos Costa(1), Julio Garcia(2), Alexandra Alvarado(3), Mónica Arcila(4), Franck Audemard(5), Carlos Benavente(6), José Cembrano(7), Gabriel González(8), Myriam López(4), Estela Minaya(9), Isabel Santibañez(7), F. Hilario Bezerra(9), Laurence Audin(10), Marco Pagani(2), Irene Pérez(12), Fabrizio Delgado(6), Mónica Paolini(5)

(1) Universidad Nacional de San Luis, San Luis, Argentina (2) GEM Foundation, Pavia, Italy (3) IG-EPN, Quito, Ecuador (4) Servicio Geológico Colombiano, Bogotá, Colombia (5) FUNVISIS, Caracas, Venezuela (6) INGEMMET, Lima, Perú (7) Pontificia Universidad Católica, Santiago, Chile (8) Universidad Católica del Norte, Antofagasta, Chile (9) Observatorio San Calixto, La Paz, Bolivia (10) Universidad Federal Rio Grande do Norte, Natal, Brazil (11) IRD-ISTerre, Grenoble, France (12) INPRES, San Juan, Argentina

Abstract: Subduction earthquakes are the most significant seismic threat for South America. However, historic destructive earthquakes related to shallow crustal sources have occurred onshore. Many important cities and critical facilities are settled nearby crustal fault sources, whose seismogenic capability is known or suspected. Despite this fact, seismic hazard assessments (SHA) have not traditionally considered potentially seismogenic faults or do so sparingly. In some cases, this is because the required fault data are absent or not available in an adequate format for SHA requirements. Recent compilation efforts such as the South America Risk Assessment (SARA) project, promoted the compilation along the region of crustal hazardous faults. This task has been undertaken to compile under homogeneous standards available information on seismically capable structures, as well as to upgrade and fulfill whenever possible key input parameters for the SARA seismic hazard source model. Many existing maps and parametric data of hazardous faults and folds in South America have relied on lineament-based terrain analysis focused on possible fault morphologies rather on the seismic capability of causative structures and uncertainties posed by data. Hence, inconsistencies in fulfilling the necessary data for SHA requirements were common. South America hosts a wide range of tectonic and morphoclimatic settings, determining different approaches for terrain analysis. Existing information has proved to be very heterogeneous in terms of geographic coverage and reliability, so data harmonization has not been straightforward. The Northern Andean Block boundary is the most prone area for large crustal earthquakes in the Northern Andes, whereas, the ~ 8.000 km-long deformation front of the Andes, is probably the most critical zone for the occurrence of large crustal earthquakes in the Central Andes. However, seismically capable structures along the last zone are still poorly known and thus, underrepresented in the available cartography.

Keywords: South America, hazardous faults, Quaternary deformation, neotectonic maps.

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Marine terraces and knickzones as proxies for uplift transients associated to megathrust earthquakes

Silvia Crosetto (1), Onno Oncken (1), Albert de Montserrat (2)

(1) GFZ German Research Centre for Geosciences, Potsdam, Germany (2) Università degli Studi di Padova, Padua, Italy

Abstract: Coastal cordilleras at subduction margins exhibit continuous to stepwise uplift occurring at a range of velocities and suggesting a possible link to the degree of offshore seismic locking. Preserved palaeoshorelines and uplifted terraces observed along the Coastal Cordillera of northern Chile show pulses of rapid transient uplift at a kiloyears time scale, likely related to clustered seismicity. Transient uplift pulses act as relative base-level drops for superficial drainage systems, causing a disequilibrium that triggers the response of the stream network. The re-equilibration response involves an increase in erosion and formation of convex river profiles and knickzones, which migrate upstream with time. The knickzone migration velocity mainly depends on drainage basin area, riverbed erodibility, and stream erosional power, the latter being controlled by precipitation rate. In the hyper-arid Atacama Desert of northern Chile, characterised by very low precipitation rates punctuated by extreme rainfall events, low knickzone migration rates allow long- term preservation of older knickzones indicative of past uplift transients. Despite the excellent preservation of landforms due to the dry climate, the analysis of knickzones’ evolution in the area is limited by the highly heterogeneous and not uniformly distributed age-data existing in literature. In a classical inverse modelling approach, this data incompleteness determines an unconstrained solution, which does not allow to ultimately define the system evolution. Therefore, we attempt a forward modelling approach: after defining a hypothetic model for the system, we test different values of the physical parameters, thus creating a set of virtual systems. The aim is to reproduce a virtual system that is able to predict the observables recognised in the natural system. If successful, this approach will highlight the strategic features that can be sampled and analysed in order to constrain the timing of the uplift pulses, possibly related to past megathrust earthquakes.

Keywords: knickpoints, marine terraces, earthquakes, stream evolution, uplift transients

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

New (And Quite Fast) Geologic Slip Rates Along Patagonia's Major and Oftentimes Concealed Crustal Strike-Slip Faults

Gregory P. De Pascale (1), Francisca Sandoval (1), Sebastian Perroud (1), Manuel Hernandez (1), Angelo Villalobos (1), Gabriel Easton (1), Daniel Moncada (1), Nicolas Buono-Core (1)

(1) Department of Geology, FCFM, University of Chile, Plaza Ercilla 803, Santiago

Abstract: Strike-slip faults play a major role in Patagonian neotectonics and seismic hazard in Southern South America. The Liquiñe-Ofqui fault zone (LOFZ) is dextral strike slip and is ~1,200 km long, whereas the Magallanes Fault System (MFS) is a Plate Boundary sinistral structure. Although they are proven seismic sources (e.g. LOFZ Mw 6.2 in 2007; MFS Mw 7.5 and 7.8 in 1949), geologic slip rates are unknown. This is partially due to dense vegetation, major Quaternary glaciations, extensive submarine portions and recent volcanism. We conducted both onshore and offshore field investigations and used remote mapping including structure from motion (SfM) models and light detection and ranging (lidar)-derived and multibeam elevation data combined with field observations. Clear LOFZ Quaternary offset streams and a novel offset glacial valley and separation of bedrock units provide dextral slip rates of 3.6–18.9 mm/yr (Late- geologic) and 11.6–24.6 mm/yr (Quaternary geomorphic). Recent fieldwork allowed us to better constrain the vertical component along the LOFZ as well (up to the east) suggesting rapid uplift directly above the subducted coincident with some of the highest peaks including the >4 km San Valentine. Along the MFS, long-term Late-Cenozoic slip rates along the main MFS fault is 5.4 ± 3.3 mm/yr based on geological separations along with two other MFS faults with ≥1 mm/yr slip rates (Deseado and Hope faults). By combining displacements observed in SfM models with regional Late-Quaternary glacial deposit ages, we obtain MFS sinistral slip-rates of 10.5 ± 1.5 mm/yr and 7.8 ± 1.3 in Chile and Argentina respectively. These fit well with previously modelled rates. Our Chilean Government (Fondecyt/CONA) supported studies provides new field- derived slip rates and a first order understanding of the neotectonics and seismic hazard in Patagonia along these fast slipping and oftentimes concealed major strike-slip faults.

Keywords: Liquiñe-Ofqui fault zone (LOFZ), Magallanes Fault System (MFS), strike slip faults, Patagonia, active faults

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Large landslides database along the Central Western Andes (15° - 20° S): constraints on mass-movement development and implications on relief evolution

F. Delgado (1,2), S. Zerathe (2), S. Schwartz (2), and C. Benavente (3)

(1) Especialidad Ingeniería Geológica, Facultad de Ciencias e Ingeniería. Pontificia Universidad Católica del Perú, Av. Universitaria 1801, San Miguel, Lima 15088, Perú ([email protected] ) (2) Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, 38000 Grenoble, France ([email protected] / [email protected] ) (3) Instituto Geológico, Minero y Metalúrgico INGEMMET, Av. Canadá 1470, Lima, Perú. ([email protected] )

Abstract: The western flank of the central Andes presents an exceptional concentration of large paleolandslides (v> 100*106 m3), most of which being well-preserved morphologies due to low erosion and weathering related to the hyper-arid climate of the Atacama Desert since the Miocene. First order questions are pending about the triggering of those mass-movements, their dynamics, their locations and their roles on the Andean relief evolution. Previous studies included geomorphological analysis and few dating on individual landslides (e.g. in Peru: Margirier et al., 2015; Crosta et al., 2014; Zerathe et al., 2017; Delgado et al., 2020; e.g. in Chile: Strasser and Schlunegger, 2005; Pinto et al., 2008; Crosta et al., 2017). Preliminary regional mapping have been attempted in Peru (Geocatmin-INGEMMET and Audin & Bechir 2006) and in Chile (Matther et al., 2014 and Crosta et al., 2014). Here we proposed a new and exhaustive mapping of large landslides of the Western Andes updating and homogenizing the previous works. The considered area locates between latitude 15° and 20°S, from the coast to the mean elevation of the (~5000 m a.s.l). The landslide mapping was done by using Google Earth and DEMs (TanDEM-X and Pléiades). We mapped polygons (surface area > 0.1 km²) corresponding to destructured areas and strictly including the evidence of major landslide scarps (cliffs, unusual slope-breaks, etc.) and its sliding mass (offset lithology, boulders fields, etc.). We identified more than 1000 landslides, distributed into three main typologies: (1) deep-seated rockslide (DSR); (2) rock-avalanche (RA) and (3) destabilizations associated with both dynamics. This GIS database allows statistical analysis and interpretations crossing the landslide distribution and typologies versus relief properties, geology-lithology, long-term uplift, dating, etc. Preliminary analysis of this database shows that spatial distribution of mass-movements is not homogeneous. Instead, we observed cluster of mass-movements following the main valleys or canyons. They mainly located at elevation between 1500 and 2000 m a.s.l. Interestingly, the largest landslides (surface area > 50 km2) are disconnected to fluvial incision. They occurred within interfluve areas. Few of the largest landslides cover alone more than 30 % of the total cumulated landslide area in this region and, on their own, might contribute at a first order to the relief erosion.

Keywords: Landslides, Central Andes

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Can the major Northern Chile Seismic Gap produce ~Mw 9.5 tsunamigenic earthquakes? Unveiling past socionatural disasters from geoarchaeological records along the hyperarid Atacama Desert at multimillennial timescales

Gabriel Easton (1), Diego Salazar (2), James Goff (3), Jean Louis Guendon (4), José González-Alfaro (1)

(1) Universidad de Chile, Geología, Santiago, Chile (2) Universidad de Chile, Antropología, Santiago, Chile (3) University of , Pangea Research Centre, School of Biological, Earth and Environmental Sciences, Sydney, Australia (4) Centre National de la Recherche Scientifique, France

Abstract: The subduction margin of the Nazca plate beneath the South American plate along Northern Chile is considered to be among the major seismic gap regions worldwide encompassing more than 1000 km between Arica (18.47ºS) and Huasco (28.47ºS). Along this major tectonic margin the last large tsunamigenic earthquakes were the Mw~8.8 1877 CE and the Mw~8.5 1922 CE events, whose rupture areas occurred along its northern and southern segments, respectively. Only limited ruptures have occurred in the Taltal segment located in the middle of this vast region (25.4ºS). The coastal Atacama Desert along this region constitutes the most hyperarid environment worldwide, inhabited since at least 12 ka by hunter-gatherers communities that developed specific strategies strongly related to the sea, and thereafter by modern societies since the 16th century but mostly since the 19th century. In spite of the scarcity of data, we used a range of multidisciplinary and multiproxy approaches in an attempt to identify paleotsunami and paleoseismological evidences, as well as to assess the impact of these kind of events on early inhabitants. From the assessment of geoarchaeological records, submarine features and uplifted littoral sediments well preserved in carefully identified sheltered environments along these dominantly rocky coasts, we identified severe paleotsunamis and associated paleoearthquakes which occurred in the XIII and in the XV centuries. More importantly, growing geological evidence and model results point to the occurrence of a Mw~9.5 tsunamigenic earthquake that caused a dramatic social disruption along this vast extremely arid coastal region around 4000 cal years BP, suggesting the capability of this major seismic gap to produce super-earthquakes and tsunamis at multimillennial timescales with significant human consequences.

Keywords: Northern Chile seismic gap, Mw9.5 tsunamigenic earthquake, Atacama Desert, socionatural disasters

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Offshore tsunami backwash deposits – a multi-proxy approach

Lisa Feist (1), Pedro J.M. Costa (2,3), Piero Bellanova (1,4), Mike Frenken (1,4), Cristina Val-Peón (1), Daniela Eichner (1), Juan I. Santisteban (5), Ivana Bosnic (2), Jannis Kuhlmann (6), Jan Schwarzbauer (4), Helmut Brückner (7), Andreas Vött (8), João F. Duarte (9), César Andrade (2), Klaus Reicherter (1), and the M152 scientific team

(1) Neotectonics and Natural Hazards Group, RWTH Aachen University, Germany (2) Instituto D. Luiz, Faculdade de Ciências, Universidade de Lisboa, Portugal (3) Earth Sciences Department, Faculty of Sciences and Technologies, University of Coimbra, Portugal (4) Laboratory for Organic-Geochemical Analysis, Institute of Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University, Germany (5) Department of Geodynamics, Stratigraphy and Paleontology, Fac. Geological Sciences, Complutense University of Madrid, Spain (6) MARUM - Center for Marine Environmental Sciences, Research Faculty, University of Bremen, Germany (7) Institute of Geography, Department of Geosciences, University of Cologne, Germany (8) Institute of Geography, Natural Hazard Research and Geoarchaeology Group, Johannes Gutenberg- Universität Mainz, Germany (9) Divisão de Geologia Marinha, Instituto Hidrográfico, Portugal

Abstract: Tsunami research has shown substantial progress during the last decades. However, many tsunami characteristics and related depositional mechanisms are as yet poorly understood. This holds especially true for offshore tsunami deposits presumably representing the backwash from land. Data for an in-depth investigation of the sedimentological characteristics and palaeo-ecological effects of offshore backwash deposits was obtained from the Algarve continental shelf (Portugal) during RV METEOR cruise M152 in November 2018. The high-intensity tsunami triggered by the AD 1755 Lisbon earthquake devastated the Algarve coast and left significant, well-studied onshore deposits, especially in the area around Boca do Rio and Sagres. Offshore from this area, eight vibracores were retrieved from 65 to 114 m water depth, in a coast-perpendicular transect. Using a multi-proxy approach, granulometry, magnetic susceptibility, P-wave velocities, inorganic (XRF) and organic (biomarkers) geochemistry, micropalaeontological and palynological data were combined. Radiocarbon and optically stimulated luminescence ages rendered the geochronological framework. At the coring site closest to the coast, deposits of the AD 1755 Lisbon tsunami were identified at a core depth of 21-24 cm. Surprisingly, another, a yet unknown, event deposit was discovered about 1 m deeper and radiocarbon-dated to ca. 3700 years cal. BP. This older event layer mainly consists of well-preserved medium- sized minerogenic sand, with a thickness of ca. 35 cm (118-153 cm core depth). It was traceable in sub-bottom profiles and in cores from two other sites, while it was missing at the furthest offshore sites. Due to the thickness of this older event deposit and its traceability in the sub-bottom profiles, the hydrodynamic conditions of its deposition could be studied. This event stratum is interpreted as the result of an offshore-directed high density hyperpycnal flow most probably related with tsunami backwash.

Keywords: AD 1755 Lisbon tsunami, offshore tsunami deposits, tsunami backwash, multi-proxy analysis

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Middle-Late Pleistocene uplift of southwestern Sicily, central : quantitative constraints on regional and local deformation processes based on raised paleoshorelines

Ferranti Luigi (1), Burrato Pierfrancesco (2), Sechi Daniele (3), Andreucci Stefano (4), Pascucci Vincenzo (3)

(1) Department of Earth Sciences, Environment and Resources (DiSTAR), University of Naples Federico II, Naples, Italy. (2) Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy. (3) Department of Architecture, Design and Planning, University of Sassari, Sassari Italy. (4) Department of Chemical and Geological Sciences, University of Cagliari, Cagliari, Italy.

Abstract: The Pleistocene coastal tectonics of Italy is relatively well understood, however the southwestern Sicily shore, which spans the frontal part of the active Sicilian and thrust belt represents a remarkable exception. We provide the first assessment of vertical deformation along a ~80 km coastal stretch in southwestern Sicily by means of mapping and luminescence aging of raised marine terraces and associated aeolian dune ridges. A staircase of twelve terraces, whose shoreline angle lies between ~10-300 m a.s.l. characterizes the gently sloping coastal plain between Capo Lilibeo and Capo Bianco. Luminescence ages from beach to shoreface deposits that mantle the terraces in the Selinunte Plain (central part of the study area) constraints the position of three paleoshorelines related to MIS 5e (~125 ka), 7a (~200 ka) and 7c (~215 ka), respectively, and provide an ~0.5 mm/yr uplift rate for the Plain. By extrapolating the computed uplift rate to lower and higher terraces, we assign the whole flight to highstands and locally interstadial stillstands of the Middle-Late Pleistocene (~80-400 ka). The terrace elevation profile parallel to the coast shows a bell-shaped pattern. Indeed, uplift rates are null in the Egadi islands east of Sicily and peak to ~0.7-0.8 mm/yr in the Menfi- Sciacca area, and then decrease to ~0.4 mm/yr at Capo Bianco in the west. Short-wavelength (~10 km long) undulations are superimposed on this broader trend. The along-coast pattern of uplifted paleoshorelines documents that coastal displacement embeds a regional and a local component. The bell-shaped pattern of uplift forms the regional component and is related to involvement in the thrust belt of thicker crustal portions of the northern African continental margin. The short-wavelength undulations represent the local component and correspond to actively growing bedrock folds. Remnants of higher (up to ~650 m a.s.l.) abrasion surfaces carved in Pliocene-Lower Pleistocene rocks and the elevation of Early Pleistocene deposits and abrasion surfaces suggests that uplift occurred at similar rates and likely with a similar pattern during Early Pleistocene, but reduced to almost zero during the late part of the Early Pleistocene.

Keywords: Coastal Tectonics, Pleistocene Marine terraces, Luminescence dating, Fold Growth, Southwestern Sicily

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Late Pleistocene and Holocene paleoseismology and deformation rates of the Pleasant Valley Fault (Nevada, USA)

Figueiredo, P.M. (1),Wesnousky, S.G.(2), Owen, L.A. (1)

(1) Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, USA (2) Center for Neotectonic Studies and Nevada Seismological Laboratory, University ofNevada, Reno, Nevada, U.S.A.

Abstract: The intra-continental Pleasant Valley Fault is the northernmost active fault in the Central Nevada Seismic Belt, an area of increased seismic activity within the Basin and Range that southwards merges into the Walker Lane. On October 2nd 1915, this fault generated a magnitude 7.3 earthquake, producing scarps with an average displacement of 2m (maximum 5.8 m) along a rupture length of roughly 60 km. This earthquake was the first of a Central Nevada Seismic Belt seismic sequence of similar magnitudes that includes the 1932 Cedar Mountain and 2 earthquakes in 1954 Dixie Valley - Fairview Peak and Fallon Stillwater. The Pleasant Valley fault system displaces several alluvial fans along the western Tobin Range mountain front, and cumulative Quaternary displacement is recognized in the landscape through older scarps. The 1915 surface rupture is expressed by four segments and the two central Pearce and Tobin segments exhibit the highest and largest scarps. We excavated five new paleoseismic trenches across the 1915 ruptures, at 4 locations distributed by the two central segments. Colluvial stratigraphy exposed in the trenches records multi-event earthquake histories at each site. The colluvial units are generally characterized by fine gravel to sandy sediments, presenting different degrees of pedogenic development, and occasionally carbonate enriched. More than 25 luminescence ages on the colluvial units and material filling fissures help define the timing of paleo surface rupture events. Analysis of the OSL dating places temporal limits on the pre-1915 surface displacements and tentatively provide evidence of 3 or 4 events prior to 1915 during the last ~45 ka. Long term deformation rates are also defined using 6 depth profiles sampled for terrestrial cosmogenic nuclide dating (10Be and 36Cl) at different locations and positions of the displaced alluvial fans present along the mountain front.

Keywords: Intra-continental seismicity, Central Nevada Seismic Belt, paleoseismicity Basin and Range

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

2011 Tohoku-oki and the historical Sanriki-oki tsunami - organic geochemical investigation of multiple tsunami deposits at the Aomori coast (Northern Japan)

Mike Frenken (1,2), Piero Bellanova (1,2), Yuichi Nishimura (3), Jan Schwarzbauer (2), Klaus Reicherter (1)

(1) Neotectonics and Natural Hazards Group, RWTH Aachen University, Germany (2) Institute for Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University, Germany (3) Institute of Seismology and Volcanology, Hokkaido University, Japan

Abstract: Japanese coastlines are the most affected areas by tsunamis in the world. Major events causing massive damage within the last century were three Sanriki-oki tsunamis (1896, 1933, 1968) and the recent 2011 Tohoku-oki tsunami. With an inundation height of 6 - 10 m at Misawa, the 2011 Tohoku-oki tsunami reached up to 550 m inland, while sandy tsunami deposits are detectable only up to 250 – 350 m of the total inundation distance. For the investigation of the “invisible” tsunami deposits beyond the visible recognition, the use of organic geochemical indicators can provide a better understanding of the extend and processes, such as the deposition and backwash. Damages during the tsunami cause the released and distributed pollutants associated with biological and anthropogenic markers. These organic geochemical compounds give the tsunami deposit a unique geochemical signature that is distinguishable from the background sedimentation. Organic-geochemical results reveal an increase of anthropogenic markers (polycyclic aromatic hydrocarbons, pesticides, chlorinated compounds) and variations of biological markers (n-alkanes, terpenes, n-aldehydes) in the 2011 tsunami deposit. During analysis, another variation of organic markers was identified right below the soil layer of the current forest. This layer is well distinguishable from the paleo-dune that marks the lowest sedimentological unit at the field site. This differentiation shows the likely impact of a historical Sanriki-oki tsunami. These organic geochemical results in combination with local eyewitness reports lead to the assumption that the sedimentary archive of the Aomori coastline contains and preserved more tsunami events of the last century. The inclusion of organic geochemical markers expands the characterization and identification of tsunamis by a powerful proxy. Furthermore, this method demonstrates the capability to detect tsunami deposits beyond the visible recognition serving as a blue-print for historical and paleo-tsunami studies, as most of them (as for yet) only rely on visible sand deposits.

Keywords: 2011 Tohoku-oki tsunami, Misawa, geochemical signature, tsunami deposits, sediment archive, historical tsunamis

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Multi-proxy investigation of the AD 1755 Lisbon tsunami deposits in Conil de la Frontera, Spain

Mike Frenken (1,2), Christoph Cämmerer (1), Piero Bellanova (1,2), Max Chaumet (1), Jan Schwarzbauer (2), Klaus Reicherter (1)

(1) Neotectonics and Natural Hazards Group, RWTH Aachen University, Germany (2) Institute of Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University, Germany

Abstract: Major inundations with sediment transport along the coastline of the Gulf of Cadiz were caused by the tsunami on November 1st AD 1755, triggered by an 8.5 to 9 MW earthquake. The study area, Conil de la Frontera (El Palmar de Vejer), located at the Gulf of Cadiz (Spain), was severely struck by the impact of the tsunami. Evidence of the inundation’s destructive power are the walls of Torre de Castilnovo, which were partially destroyed. The characteristic alluvial flood plain El Palmar de Vejer was chosen as a study area. With its peculiarities, the area presents a well-preserved sedimentary archive for deposits of the AD 1755 tsunami. Ground-penetrating radar (270 MHz antenna) was used to systematically identify the sandy layers attributed to tsunami events in depth up to 3 m. Granulometric analyses were carried out (1) to identify the sandy tsunami deposit; (2) to analyse the different depositional environments before, during and after the tsunami; (3) to detect tsunami sublayers deriving from different waves within the AD 1755 tsunami wave-train and (4) to identify other extreme wave events in the geological record. Analysis of major elements (Ca, Ti, Fe, Sr, K) as well as elemental ratios is used to identify a distinction between marine and terrestrial depositional environments and source material. Several distinctions between the AD 1755 deposits and surrounding background sediments are indicated by different natural compounds (e.g., n-alkanes, n-aldehydes), detected via organic geochemical biomarker analysis. The tsunami deposits contrast mainly through varying concentrations and deviant occurrence of specific compounds (marine vs. terrestrial). This study presents strong evidence that a multi-proxy approach with the inclusion of geochemical applications can confidently detect and distinguish tsunami deposits of the AD 1755 Lisbon tsunami from surrounding background sediments

Keywords: AD 1755 Lisbon tsunami, El Palmar de Vejer, floodplain, tsunami sediments, successive waves, tsunami wave cycle

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Spatial variations in rock uplift rates in the Colca River basin inferred from landscape analysis and river terraces dating, Central Andes

Krzysztof Gaidzik (1), Kevin R. Sanchez Garcia (2), María Teresa Ramírez-Herrera (2), Laurence Audin (3), Jerzy Żaba (1), Justyna Ciesielczuk (1)

(1) Institute of Earth Sciences, University of , Będzińska 60, 41-200 Sosnowiec, Poland. E-mail: [email protected] (2) Tsunami and Paleoseismology Lab., Instituto de Geografía, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán, 04510 México, DF, México (3) Université Grenoble Alpes, ISTerre, Grenoble, France

Abstract: In this study, we aimed to recognize the spatial variations of uplift rates across the forearc of the Nazca-South America subduction zone using landscape analysis. For that, we focused on the Colca basin that presents striking differences in topography and high seismicity resulting from 1) megathrust earthquakes, 2) shallow seismic events triggered by active crustal faults, and 3) volcanic microseismicity and tremors. To assess spatial variations in uplift rates basin we applied 1) observations from the field, 2) calculation of selected geomorphic indices, and 3) river terraces dating. We calculated the following indices: topographic swath profiles, river longitudinal, and transverse profiles, stream-length gradient index, minimum bulk erosion, hypsometric integral and curves, low order stream gradients, drainage density, sinuosity index, valley height- width ratio, dissection index, relief energy, asymmetry factor, and basin elongation ratio. The resulting longitudinal profile shows several abrupt breaks in the slope that do not correlate with changes in bedrock lithology. Transverse profiles, together with values of sinuosity index, stream-length gradient index, river gradient, and valley width to valley height ratio indicate at least four sections along the trunk river with different valley shape, and diverse local relief. High relative erosion and a vertical incision are suggested for the intermediate part, where anomaly high values of stream-length gradient index, dissection index, relief energy, low order stream gradients, and minimum bulk erosion were recorded. This confirms the field observations and high uplift derived from the strath terraces dating, as it coincides with the deepest section of the basin known as the Colca Canyon. Lack of correlation between the observed pattern and variations in bedrock lithology suggests additional tectonic forcing. Finally, the observed variations in the geomorphic indices seem to corroborate the importance of the left-lateral transpressional Incapuquio Fault System structuring the front of the Western Cordillera in southern Peru.

Keywords: Rock uplift, landscape analysis, geomorphic index, river terrace, Central Andes

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Analysis of the Damage Orientation of the 1950 Earthquake in Cusco City

Garcia, B. (1), Benavente, C. (1), Rosell, L. (1) and Palomino, A. (1)

(1) Instituto Geológico Minero y Metalúrgico. [email protected]

Abstract: Cusco Valley, where Pre-Inca and Inca cultures settled, is a cultural heritage with more than half million people. The city of Cusco is located at south of Tambomachay, Pachatusan and Qoricocha faults, the most important segments. These EW structures generated historical earthquakes >6M (1650 and 1950 AD). Cusco’s floor is composed by lacustrine and alluvial deposits from San Sebastian Formation. Therefore, the lithology and active faults relation represent an important geological hazard for this city. The last seismic event (1950) let more than a thousand dead people and destroyed partially Cusco city, mainly colonial churches, monuments and some Inca walls. Due to the poor seismic network of the time, it was not possible to accurately determine the epicenter of the earthquake. After earthquake, some specialists recorded co-seismic effects to considered VII as maximum intensity in epicentral area. Thus, in order to determine the direction of the epicenter location and confirm the degree of intensity of the earthquake, we returned to Cusco, mainly the city center, to took more than seventy oriented measures (wall collapsed and tilted direction, dipping broken corners, dropped stones in arcs, fallen columns and statues, conjugated and penetrative fractures), for this task, we based on historical documents and photos, that recorded damages in colonial churches, cloisters, houses, historical monuments, and some Inca walls. Surprisingly, the greatest damage is recorded in colonial buildings, the damage in Inca buildings are very few, thanks to the type of earthquake-resistant construction that this culture developed. Data suggest that the main damage orientation is 330N, another minor trend is 50N. These damage orientation is related to seismic wave direction arrival, as well as they are related to the faults location. Finally, based on ESI07 and EMS98 scales of Earthquake Archaeological Effects we suggest that the intensity in epicentral area was IX.

Keywords: Damage, 1950 earthquake, Cusco, Peru

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Collisional Indenter Tectonics of the Santa Ana Mountains and the Southern Los Angeles Basin, Orange County, California

Eldon Gath (1)

(1) Earth Consultants International - [email protected]

Abstract: The Santa Ana Mountains (SAM), a plutonic-cored intrusive body dominating Southern California’s Orange County landscape, are being thrust into the sediment-filled Los Angeles Basin at 5-6 mm/yr by the right-lateral Elsinore fault. This SAM indenter has resulted in ~18 km of Plio-Pleistocene-age, northwest vergent, penetration through the Cretaceous to Pleistocene sedimentary section generating multiple secondary tectonic geomorphic structures including strike-slip faults, anticlines, imbricate thrust sheets, and disseminated secondary faulting and fracturing of the surrounding rocks. Simultaneously, the south vergent Puente Hills are uplifting along a blind Puente Hills . As these two structures converge, the uplift rate of the Puente Hills is increased, the right-lateral Whittier fault accommodates westward escape tectonics of the basin sediments at 2-3 mm/yr, and 1-2 mm/yr left-lateral shearing is developed within a weak shale unit along the western SAM margin due to weak coupling of the sedimentary rocks and the plutonic indenter. Microseismicity is concentrated within the deforming sedimentary section above and in front of the indenting pluton, reactivating pre-existing secondary faults and posing a regional ground deformation (and seismic shaking) hazard to the 3+ million people of Orange County, California.

Keywords: Collisional Indenter Tectonics, Santa Ana Mountains, California

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

1909 Benavente Earthquake (Intensity X, Portugal): Seismic source determination through geological effects

C. Canora (1), J.L. Giner-Robles (1), J. Elez (2) and P.G. Silva (2)

(1) Dpto. Geología y Geoquímica, Facultad de Ciencias, Universidad Autónoma de Madrid. Campus de Cantoblanco, 28049 Madrid. [email protected]; [email protected] (2) Dpto. Geología, Facultad de Ciencias, Universidad de Salamanca. 37008 Salamanca. [email protected]; [email protected]

Abstract: The Environmental Seismic Intensity Scale (ESI-07) appeared after the exclusion of natural effects for intensity assignments in the new European Macroseismic Scale (EMS-98). This scale allows the evaluation of the intensity exclusively from earthquake environmental effects (EAEs), applicable in unpopulated areas without buildings, areas where damage has been saturated by extensive devastation and of use for any historical or prehistoric period. The scale provides a quantitative intensity assessment from geological, hydrological, geomorphological and environmental anomalies associated with each of the intensity degrees (Guerrieri and Vittori, 2007). The EAEs featured in the ESI scale provide essential information for seismic source assessment, especially for historical earthquakes where the intensity values are calculated trough building damage, no sufficient for source location. The 1909 Benavente earthquake (Intensity X) is one of these cases. This event devastated at least seven towns (most of the buildings collapsed or were demolished), producing saturation on the MM intensity scale. On the other hand, the intensity data for the epicentral area are quite biased due to the existence of large crop areas (barely populated) and an unequal geographical distribution of populations on both sides of the Tagus Valley. This paper presents the ESI-classification of the variety of EAEs described in the field report produced by Choffat and Bensaude, (1912), to explore the most feasible location for the responsible seismic source.

Keywords: 1909 Benavente earthquake, seismic source, Portugal

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Paleoseismic evidence in multiple fault-branches across a transect of the Alhama de Murcia Fault (SE Spain)

Octavi Gómez-Novell (1), María Ortuño (1), Julián García-Mayordomo (2), Eulàlia Masana (1), Raimon Pallàs (1), Juan Miguel Insua-Arévalo (3), José Jesús Martínez-Díaz (3) Thomas Rockwell (4), Stéphane Baize (5)

(1) RISKNAT Group, Facultat de Ciències de la Terra, Universitat de Barcelona, 08028 Barcelona, España (2) Instituto Geológico y Minero de España, 28760 Tres Cantos, España (3) Departamento de Geodinámica, Estratigrafía y Paleontología, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid, 28040 Madrid, Spain (4) Department of Geological Sciences, San Diego State University, 92182 San Diego, California, EUA. (5) Institut de Radioprotection et Sûreté Nucléaire – Seismic Hazard Division (BERSSIN), 92262 Fontenay- aux-Roses, Francia

Abstract: We present a comprehensive paleoseismological study across a transect of the Alhama de Murcia Fault (AMF) in the segment between Lorca and Totana cities (LT). The AMF is one of the most active faults within the Eastern Betics fault system, responsible for several damaging earthquakes. In the LT segment, the fault shows a complex structure with at least five branches, only one of them (S-AMF) studied to date. We conducted paleoseismic trenching in three of the non-previously studied branches of the segment (N1-, N2- and f-AMF) in order to understand their activity degree. Trench analysis provided evidence of recurrent Quaternary activity in the three branches with a minimum of 5 identified paleoevents in each. The last one, in f-AMF, is younger than 8-9 kyr BP, based on radiocarbon dates. We also dug an exceptionally large trench (7 m deep) in S-AMF to enlarge the paleoearthquake record of previous studies. 13 paleoevents have been interpreted, which is the completest paleoseismic record to date for the AMF. The tectonic structures in the trenches and the geomorphic expression of the fault suggest that the deformation is partitioned between the different branches. S- and N1-AMF absorb the main strike-slip component, while N2-, and especially f-AMF, accommodate the dip-slip component. Despite this, vertical displacement is relevant in most of the branches, as suggested by the measured vertical offsets and the restored trench cross sections. This study allows for an improved characterization of the AMF, formerly inferred from a single branch. Forthcoming numerical dates will allow for a reassessment of the recurrence intervals and slip rates, and for the evaluation of a possible synchronic behaviour of the branches. The integral characterization of the fault structure and deformation throughout the studied transect will also improve the source modelling for fault-based probabilistic seismic hazard analyses of the region.

Keywords: Alhama de Murcia Fault, paleoseismology, fault branches, slip partitioning, integral fault characterization

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Slip rates variability along an irregular normal fault plane: Accelerated uplift accommodation during the late Quaternary, Mejillones Peninsula, northern Chile

J. González-Alfaro (1), G. Easton (1), G. González (2), B. Sylvain (3), G. Gabalda (3), G. Álvarez (4), F. Leyton (5), B. Huerta (4), J. Valdenegro (4)

(1) Departamento de Geología, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Plaza Ercilla 803, Santiago, Chile. [email protected] (2) Departamento de Ciencias Geológicas, Centro Nacional de Investigación para la Gestión Integrada de Desastres Naturales (CIGIDEN), Universidad Católica del Norte, Avenida Angamos 0610, Antofagasta, Chile. (3) GET/UMR5563 (UPS, CNRS, IRD, CNES); Obs. Midi-Pyrénées, Université P. Sabatier, Toulouse, France. (4) Departamento de Ingeniería en Geomensura y Geomática, Facultad de Ingeniería, Universidad de Antofagasta, Avenida Universidad de Antofagasta 02800, Antofagasta, Chile. (5) Centro Sismológico Nacional, Universidad de Chile, Blanco Encalada 2002, Santiago, Chile.

Abstract: In paleoseismology, choosing the better place to dig a trench along a fault trace it is a difficult decision that may influence ulterior slip rate estimations. Over or underestimation slip rates along a fault trace may induce errors in the magnitude and recurrence intervals in a worse-case scenario for seismic hazard evaluation; even further when the fault geometry is quite irregular along-strike. Although this problem is present in several study cases, using morphometric analysis in deformed surfaces could minimize slip rate uncertainties. In this work, we take as example the Mejillones Fault located in northern Mejillones Peninsula, at the southern edge of the northern Chile seismic gap. We analyzed the landforms in the hanging wall of this fault, such as tilting paleo-beach ridges and the last glacial maximum (LGM) submerged platform, in addition with swath profiles covering both subaerial and submarine fault scarps, and geomorphological features. We characterized fault and folding affecting the Neogene substratum and Pleistocene sedimentary infill of the Mejillones Bay. Our results show a variability in the fault throw along the trace of the Mejillones Fault, which increase from south to north. The slip variability is consistent with a wider extension of the deformed surface area from south to north, which is manifested as hanging wall tilting toward the fault, and would demonstrate a fault plane scissors geometry. The hanging wall deformation has been greater both fault northward and at least since the middle Pleistocene. This would evidence the direct relationship between the fault activity and an accelerated uplift rate over the late Quaternary. Considering PGA models from fault plane segments of the Mejillones Fault System, the intensity and location of maximum accelerations lead to different results that imply different scenarios for seismic hazard assessment.

Keywords: Slip rates variability, accelerated uplift, Mejillones Fault, northern Chile

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Structural and seismic segmentation of the Coastal Cordillera in Northern Chile: a general overview and the linking processes

Gabriel González (1), Yerko González (1), Francisco Pastén (2) and Pablo Salazar (3)

(1) Centro de Investigación para la Gestión Integrada de Desastres, Departamento de Ciencias Geológicas Universidad Católica del Norte. (2) Departamento de Geofisica, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile

Abstract: The style of faulting of the Coastal Cordillera in northern Chile (25º-18.5ºS) evidences a structural segmentation consisting of the prevalence of trench parallel faults southward of 21.5ºS and the occurrences of a mesh of regional scales faults given by trench-orthogonal and trench-oblique faults northward this latitudinal limit. The structures south of 21.5ºS are mainly related to normal faulting whereas those exposed in the northern segment are dominated by NS shortening. The segment boundary is given by a major EW striking reverse fault termed Aguirre Fault, exposed at 21.5ºS. The deployment of local short-period seismic networks and the permanent broadband stations of the plate boundary IPOC observatory (https://doi.org/10.14470/PK615318) shown that the northern segment concentrates upper plate seismicity whereas the southern segment is devoid of this type of events. In the northern segment, focal mechanisms reveal that upper plate earthquakes are dominated by trench parallel shortening, with fault mechanism consistent with strike-slip and reverse faulting. In contrast, southward of 21.5ºS, there are not focal mechanisms available for the major trench-parallel faults. On September 11th of 2020, an Mw 6.2 earthquake reactivated the deepest section of the Aguirre Fault highlighting that this fault extends from the topographic surface to the bottom of the upper plate. Fault mechanism for the mainshock and the aftershocks evidences that this earthquake was caused by NS shortening. Previous authors noted that the upper plate seismicity beneath this fault form an upward curved limit, where the upper plate seismicity disappears to the south. In cross-section, the aftershocks related to the Mw 6.2 earthquake alienate along this structure showing that the Aguirre Fault and the upward curved structure are the same features. Consequently, we propose that the Aguirre Fault makes the segment boundary either for the structural segmentation as well as the seismic the segmentation of this cordillera.

Keywords: Coastal Cordillera, northern Chile, structural segmentation, upper plate faulting

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

New marine terraces 10Be exposure ages in the central-eastern part of the Mejillones Peninsula, northern Chile.

Yerko González (1), Gabriel González (1), Vincent Regard (2)

(1) CIGIDEN (Centro para la investigación y gestión integrada de desastres naturales), Universidad Católica del Norte, Antofagasta, Chile. (2) GET, Unviversity of Toulouse, UPS, CNRS, IRD, CNES, Toulouse, France.

Abstract: In this work, we discuss new exposure ages of three uplifted shore platforms. These shore platforms are part of a well-preserved staircase marine terrace sequence carved over the western flank of Morro Jorgino horst in Mejillones Peninsula (22°S). We obtained ages using 10Be cosmogenic nuclides method, following the sampling strategy of vertical concentration profiles using a Monte Carlo simulation designed in Matlab. During the fieldwork, we recollected quartz veins from the surface of marine terraces (without sediment cover) called T6, T4, and T3 at the heights of 113, 147, and 218 m.a.s.l respectively. For each marine terrace surface, 5 samples were collected at regular depths from the surface to a depth of 2 meters. The T6 age computed from the profile inversion is 481 ky (-62 ky, +61 ky), which is related to the MIS 13 (480 ky). The computed T4 age is 514 ky (-24 ky, +124 ky) which could correspond either to MIS 13 or MIS 15 (570 ky). Conversely, on the eastern flank of the horst, a reworked ash layer (672.7 + 43.9 ky by Ar40/Ar39) is covering the top of shallow marine sediments of T4, which indicates that T4 was formed during MIS 17 (690 ky). In this case, we assume that 10Be dating is less accurate than Ar40/Ar39 ash dating, which could mean that T4 is more related to MIS 17 than MIS 15 or MIS 13. T3 is 531 ky (-21.5 ky, +273 ky). Between this age range, three interglacial stages were developed, MIS 15, MIS 17, and MIS 19 (780 ky). The most likely is MIS 19, considering that MIS 17 is assigned for T4. These results indicate uplift rates of 0,3-0,4 m/ky over the last ∼780 ky, high enough to achieve the preservation of different and continuous MISs during the Pleistocene.

Keywords: Cosmogenic nuclides, marine terraces, coastal uplift, Mejillones Peninsula, northern Chile.

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Geomorphological map of the Quaternary deposits of Península de Mejillones, Antofagasta (Chile).

J.L. Goy (1), C. Zazo (2), T. Bardají (3), A. Martínez-Graña (1), C.J. Dabrio (4), P.G. Silva (1), Cl. Hillaire- Marcel (5), J. Lario (6), E. Roquero (7), L. Ortlieb( )

(1) Dpto. Geología; Universidad de Salamanca. 37008-Salamanca. [email protected]; [email protected]; [email protected] (2) Geología; Museo Nal. CC. Naturales; CSIC. 28006-Madrid. [email protected] (3) Dpto. Geología, Geografía y Medio Ambiente; Universidad de Alcalá. 28805-Alcalá de Henares. [email protected] (4) Dpto. Estratigrafía; Universidad Complutense de Madrid. 28040-Madrid. [email protected] (5) GEOTOP, Univ. Du Québec à Montréal, 8888-Montreal, Canada. [email protected] (6) Dpto. CC. Analíticas, Fac. Ciencias; UNED. 28040-Madrid. [email protected] (7) Dpto. Edafología; ETSI Agrónomos; Universidad Politécnica de Madrid; 28040-Madrid. [email protected] ( ) In memoriam

Abstract: A geomorphological map of the Quaternary deposits has been prepared on the basis of Sc. 1:33.000 aerial photography. The methodology applied follows the classical one with the most relevant geomorphological forms being represented by symbols in the conventionally adopted colors of each morphogenetic system. In addition to the morphogenetic symbol, a textural pattern may be added. Ages are identified by different colors. Special attention has been paid to marine, alluvial and morphostructural systems, with specific symbols for morphostructural elements originated by recent active faults. The geomorphology and distribution of Quaternary deposits along Peninsula de Mejillones is strongly conditioned by an active structural framework with N-S trending faults as the main geomorphological drivers, and NW-SE and NE-SW ones as subsidiary faults. The Peninsula is characterized morphologically by a series of horsts and grabens separated by large N-S trending fractures (Mejillones Fault, Cerro Moreno Fault, etc.) and NW-SE and NE-SW secondary ones that delimit raised (Morro Mejillones, Cerro Moreno) and dropped down semigraben (e.g. Pampa Mejillones, Pampa Moreno) blocks. The best represented Quaternary deposits in the Peninsula are marine coarse sediments, with fossil mollusk fauna, represented by beach ridges (1-2m high) separated by almost 50m long swales, and reaching inland around 200m in elevation. At Pampa Mejillones, the lasts interglacials (MIS 5, 7, 9, 11) crop out between +15m for MIS 5 and +160m for MIS 11, this last one with warmer fauna than the younger ones (Ortlieb et al., 1995; Guidebook Annual Meeting IGCP367). Considering this chronology, an Early Pleistocene age can be suggested for the beginning of beach ridge systems. Alluvial fans are the second most significant deposits, which accumulated adjacent to mountain front faults (Coastal Range), where a variety of geomorphological features indicative of active tectonics (faceted faces, fault trenches, etc.) have been identified.

Keywords: Geomorphological mapping; Quaternary deposits; Península Mejillones

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Active tectonics of the Alps-Dinarides transition zone

Grützner, Christoph (1), Jure Atanackov (2), Petra Jamšek-Rupnik (2), Klaus Reicherter (3), Sumiko Tsukamoto (4), Kamil Ustaszewski (1), Blaž Vičič (5), Marko Vrabec (6)

(1) Friedrich-Schiller-Universität Jena, Institute of Geological Sciences, 07749 Jena, Germany, [email protected] (2) Geological Survey of Slovenia, 1000 Ljubljana, Slovenia (3) RWTH Aachen University, Institute of Neotectonics and Natural Hazards, 52064 Aachen, Germany (4) Leibniz Institute for Applied Geophysics, 30655 Hanover, Germany (5) The Abdus Salam International Centre for Theoretical Physics, 34151 Trieste, Italy (6) University of Ljubljana, Department of Geology, 1000 Ljubljana, Slovenia

Abstract: The transition zone between the Southern Eastern Alps and the Dinarides (NE Italy and W Slovenia) is characterized by a change from E-W striking thrust faults to a right-lateral strike-slip fault system with NW- SE directions. Geodetic data reveal that there is only 2-3 mm/yr of convergence between Adria and Europe. Instrumental seismicity is moderate and very few historical earthquake exceeded M6 in the past 1000 years. Only one event, the 1511 Idrija earthquake, is reported to have caused surface ruptures, but its location and number of causative faults are still a matter of debate. Here we present observations from tectonic geomorphology, fault mapping, paleoseismological trenching, shallow geophysics (georadar, electric resistivity tomography), and dating of Quaternary deposits (radiocarbon, luminescence dating). We especially profit from the availability of high-resolution LiDAR data for our study area. Our results show that at least three strike-slip faults have had surface-rupturing earthquakes since the last glacial maximum (LGM). Several other strike-slip and thrust structures deformed (post-)LGM deposits or landforms by earthquakes, by creep, or by a combination of both. Combining all available information from the literature and our own study, we conclude that an array of several right-lateral faults accommodates the present-day plate motion between Adria and Europe. At least seven, but perhaps more, active faults share the crustal deformation. As a result, each of these structures has a very low slip rate. However, many of these faults have the potential to rupture in strong, but rare earthquakes. This poses a challenge for tectonic studies as well as for seismic hazard assessments. Our study is part of the Priority Programme SPP2017 - Mountain Building processes in 4D funded by the German Science Foundation DFG: www.spp-mountainbuilding.de.

Keywords: Active tectonics, Alps-Dinarides transition

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Geomorphology of the cumulative deformation since Oligocene age on the Mw 4.9 Le Teil earthquake fault (South of France,11/11/19)

E. Hannouz (1), C. Sue (1, 2), S. Baize (3), J. Ritz (4), M. Ferry (4), L. Audin (1), A. Combey (1), C. Larroque (5), A. Walpersdorf (1), A. Lemoine (6)

(1) ISTerre, Grenoble, France (2) Chrono-environnement, Besançon, France (3) IRSN, Fontenay-aux-Roses, France (4) Geosciences Montpellier, Montpellier, France (5) Geoazur, Valbonne, France (6) BRGM, Orléans, France

Abstract: The Mw 4.9 earthquake (B.Delouis, Geoazur) occurring near of Montelimar on November 11, 2019 showed peculiar characteristics: a very shallow hypocenter (1-2km depth) (B.Delouis, Geoazur) resulting in surprising surface ruptures for such moderate magnitude, and only few aftershocks showing low magnitudes (ML < 2.7). This event occurred in the industrialized (including nuclear power plants and chemical industry) Rhone Valley where several historical earthquakes with similar intensities, magnitude and depths (e.g. 1773, 1873, 1934) (SISFRANCE). The earthquake broke a 5 km long segment of the northern tip of the Cevennes fault system. This ~100 km long fault network has a NE-SW orientation trend and is inherited from the Variscan (~300 Ma). It first registered an extensive and transtensive tectonic phase during the Oligocene age (~30 Ma) (Séranne et al., 1995) before being inverted, as revealed by the reverse focal mechanism of the Le Teil event. To date, this fault network has been poorly investigated in terms of its impact on seismic hazard. Therefore, we started a new study to figure out its paleo-earthquake history in the framework of the new French RGF program (Alps and surrounding basins, BRGM). Our first target was to image the cumulative trace of the fault. A first set of LiDAR images was acquired by helicopter and UAV (unmanned aerial vehicle) just after the earthquake. They allowed the identification of a continuous scarp of 1 – 2 m high over 4 km along the pre-existing Oligocene fault. In order to first characterize the post-Oligocene deformation of this fault, we then performed a detailed analysis of geomorphological field observations, as well as a geophysical study by acquisition of seismic, electrical and radar profiles. Each step of the analysis aims at eventually locate sites for further paleoseismological trenches. This kind of investigation will provide information on the evolution over time of the seismic activity of this fault network, as well as relevant data on the current hazard they present in the specific context of the French Rhone Valley.

Keywords: Geomorphology, deformation, Le Teil earthquake, France

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Is the Billecocha fault system (Northern Ecuador) a case where strike slip faulting interacts with mountain scale gravitational deformations? Insights from morphological and paleoseismological investigations

Jomard H. (1), Saqui D. (2), Baize S. (1), Alvarado A. (2), Bernard B. (2), Audin L. (3), Hidalgo S. (2), Pacheco D. (2,4), Ruiz M. (2) and Segovia M. (2)

(1) 1Institut de Radioprotection et Sûreté Nucléaire, 92262 Fontenay-aux-Roses, France (2) Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN), Ap. DI. 01-2759, Quito, Ecuador (3) Institut des Sciences de la Terre, IRD: UR219, Université Joseph Fourier–Grenoble I–INSU–OSUG, Grenoble, France (4) Géoazur, CNRS, Université Côte d’Azur, IRD, Observatoire de la Côte d’Azur, Valbonne, France,

Abstract: The Billecocha plateau (Ecuadorian Andes – 4000m) surrounds the interandean valley located 2000m downstream. It is bordered South and North by Cotacachi and Chachimbiro active volcanoes, respectively. Both plateau and volcanoes are heavily affected by active faulting with straight, sharp and discontinuous scarps running within a 7km wide corridor, over a 25km length. The so-called Billecocha fault system (BFS) has a N030°E direction, superimposed over the Pujili suture, considered here dextrally reactivated (Alvarado et al., 2016). However, field evidences of normal motion led Ego et al. (1996) to consider the BFS as related to postglacial debutressing or gravitational deformations. In 1868, a M≈7 earthquake struck the area; the distribution of macroseismic intensities beeing compatible with an occurrence nearby the BFS (Beauval et al. 2010). We performed (1) morphological DEM/field analysis to analyse Holocene markers of active faulting and (2) paleoseismological investigations along the main fault segment to explore the coseismic character of deformations. Our main observations are: • In trenches, colluvial wedges together with evidences of both normal and transcurrent faulting reveals the coseismic character of the observed deformations. At least 3 events are observed for the last 10ky, the last being compatible with the 1868 earthquake (post 1515 cal. AD); • Most of the Holocene deformations are compatible with normal motions distributed along the BFS, while cumulative strike slip evidences are more tenuous. However, there is no clear long term evidence of relief- building; We then suggest the BFS to represent a transcurrent seismogenic structure along which gravitational processes lead to enhance the surficial expression of tectonic deformations. Two complementary observations could support this hypothesis (1) typical sackung features affect the mountain slopes toward the interandean valley and (2) evidences of Holocene reverse faulting are present in the vicinity of the BFS main fault strand, compatible with its transcurrent tectonic behaviour.

Keywords: Billecocha fault system, Ecuador

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Characteristics of the topographical deformation in the central part of the Ulsan fault

Taehyung Kim (1,2), Hyeon-Cho Shin (2), Young-Seog Kim (1,2,)

(1) Dept. of Earth & Environmental Sciences, Pukyong National University, Korea (2) Active Fault & Earthquake Mitigation Institute, Pukyong National University, Korea

Abstract: The Korean peninsula with low tectonic activity and high denudation rate is located on the continental margin away from the plate boundary. Without earthquake involving surface rupture, it is much challenging to trace active faults in this area. Therefore, paleoseismology studies in this kind of tectonic environment must rely on the synthetic process combining various approaches, including topographical characteristics related to past surface deformations. Since the installation of modern seismographs in Korea, large earthquakes with surface rupture have not occurred on the Korean Peninsula. However, there are several reported shreds of evidence for the paleoseismological and historical earthquakes with surface ruptures on the Korean peninsula. This study analyzed the distribution and activity characteristics of active faults, based on the topographic survey in the eastern part of the Ulsan fault zone, where several reported Quaternary faults are concentrated. The research area is a mountainous area on the eastern side of the Ulsan Fault. The basement of this area is composed of biotite granite. The topographic analysis revealed that the alluvial fans along the western side of the ridge developed at a similar altitude. This phenomenon indicates that the development of the fans is related to faulting. These alluvial fans are classified into three surfaces based on their elevations, indicating the effect of repetitive tectonic activities. The eastern blocks of the fan surfaces along the N-S trending lineament are commonly uplifted. The anomalies based on the electrical resistivity survey across the lineament are well consistent with the topographical anomalies. Also, the surface field survey supports east- dipping thrust faults, which cut the Quaternary alluvial fan deposits at the same anomaly points. Therefore, the thrust fault movement forms the landform of the study area.

Keywords: Deformation, Ulsan fault

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Earthquake clustering along strike-slip fault system A rule rather than an exception

Y. Klinger (1), T. Rockwell (2) H.Bhat (3)

(1) Université de Paris, Institut de physique du globe de Paris, CNRS, Paris, France, [email protected] (2) Geol. Sci., San Diego State Univ., San Diego, CA 92182; [email protected] (3) Ecole Normal Superieure Paris, Paris, France, [email protected]

Abstract: The recurrence time of earthquakes is the keystone of earthquake hazard assessment. Paleoseismological investigations typically address earthquake recurrence at one specific site where the goal is to have the longest possible time series to ensure that the average time interval, and associated standard deviation, between successive earthquakes is meaningful. Although the results might appear cluttered to some degree by natural variability, along many faults, independently of the style of deformation involved, subduction, strike-slip, or normal faulting, quasi-periodic behavior has been considered to be a reasonable model to describe occurrence of earthquakes through time. Indeed, this model is at the heart of a majority of earthquake hazard models, although it is not always explicitly mentioned. Hence, any significant departure from the average duration between successive earthquakes, as for example along the southern San Andreas fault or the fault, two major plate boundaries, rises excessive wariness about the long overdue “big one”. In the recent years, however, the accumulation of data along entire fault systems suggests a different picture that fosters a paradigm change. Data along large strike-slip fault systems indicate that these systems tend to rupture in short seismic cascade, forming spatio-temporal clusters, which are separated by longer seismically quiescent periods. The almost total rupture of the North Anatolian fault system during the XXth century initially hinted at such possible behavior, which is now recognized more and more often along major strike-slip fault systems, such as the Dead Sea fault, the Kunlun fault, the Alpine fault, or the Southern San Andreas fault systems. Thus, this accumulation of consistent observation suggests that earthquake cascades along strike-slip faults systems might be the rule rather than the exception.

Keywords: Strike-slip, earthquake return-time, earthquake cycle

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

The Truckee fault zone, California USA: Distributed active faulting in the northern Walker Lane

Rich D. Koehler (1), and I. Pierce (2)

(1) Nevada Bureau of Mines and Geology, University of Nevada, Reno, 1664 N. Virginia St., MS 178, Reno, Nevada, USA 89557 (2) Department of Earth Sciences, University of Oxford, OX1 3AN, United Kingdom

Abstract: The Truckee fault zone extends obliquely across the eastern flank of the Sierra Nevada in the northern Walker Lane tectonic province, USA, forming a kinematic link between active normal faults in the Lake Tahoe region and the right-lateral Mohawk Valley fault. The northern Walker Lane accommodates ~5-7 mm/yr of dextral shear; however, the relative rate of deformation and earthquake history of the Truckee fault zone is poorly characterized. The Truckee fault zone is structurally complex and has generated several moderate historical earthquakes (1966 M6.6 and two ~M6 earthquakes in 1914 and 1948). The system includes the northeast-trending left-lateral Dog Valley fault, the northwest-trending right-lateral Polaris fault, and numerous subparallel normal oblique faults. Here, we present geomorphic mapping observations along the Truckee fault zone based on interpretation of lidar data and preliminary paleoseismic trenching results. Preliminary results indicate that the Truckee fault zone comprises a series of distributed faults that accommodate oblique shear by transtensional deformation in the south and transpressional deformation north of the Town of Truckee where the system steps left to the Mohawk Valley fault. Tectonic geomorphic features indicative of latest Pleistocene deformation include normal and lateral displacements of glacial moraines and outwash channels, as well as aligned linear swales, scarps, and benches. Stratigraphic and structural relations exposed in a trench across the Dog Valley fault show clear truncations and progressive deformation of bedded fluvial and peat deposits and provide evidence for the occurrence of at least two latest Pleistocene/Holocene events. Radiocarbon analyses are in process. Based on 3D excavations of a prominent channel margin, the most recent earthquake was associated with ~ 1 m of left- lateral displacement. This ongoing work will contribute towards a better understanding of regional seismic hazards and the role of the Truckee fault zone in accommodating strain in the northern Walker Lane.

Keywords: Mapping, trenching, northern Walker Lane

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Re-assessing the probabilistic fault displacement hazard for distributed faults: it’s normal to make a fault.

Livio F.(1), Ferrario M. F.(1), Michetti A.M.(1)

(1) Università dell’Insubria, Dipartimento di Scienza ed Alta Tecnologia, via Valleggio 11, Como (Italy)

Abstract: Fault displacement hazard assessment (FDHA) is based on the analysis of empirical datasets. Apart the FDHA of primary seismogenic faults, an increasing interest is recently growing on the evaluation of distributed faulting due to recent technological advancements and the availability of data with unprecedented resolution. It is thus time to re-evaluate the commonly adopted probability relations on distributed faulting occurrence (e.g., Youngs et al., 2003) in a prospective way, with the additional support of recent well- documented earthquakes, previously overlooked or more recent than the published works. We collected published data on 21 normal faulting surface-rupturing earthquakes occurred between 1887 and 2016. In order to check the accuracy of known probabilistic FDHA relations, we computed the conditional probability of faulting occurrence as a function of distance from the primary fault, following the same methods adopted by Youngs et al. (2003). Current scaling relations tend to underpredict the actual occurrence of rupture, if considered as a prediction equation for engineering purposes (i.e., a conservative estimate of where and how much will occur). We found no clear dependencies on the time of occurrence (“old” vs “modern” datasets) and magnitude range. The main factor affecting the results is the resolution at which data are analyzed: adopting a coarse resolution (e.g., grid size of 500 m for normal faulting events, as done by Youngs et al., 2003), there is no significant difference between modern and old case histories. Otherwise, improving the spatial resolution may introduce a time- dependent bias (as also observed by Petersen et al., 2013) preventing a direct comparison among events occurred tens of years apart. This fact must be considered when developing the new generation of scaling relations. Our analysis contributes to the recent efforts to constitute a worldwide and unified database for fault rupture analyses (e.g., SURE database, Baize et al., 2019).

Keywords: Surface faulting, distributed faults, FDHA

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Integration of faults, earthquakes and geodetic data for estimating PSHA: the Italian model.

C. Meletti (1), W. Marzocchi (2), V. D'Amico (1), G. Lanzano (1), L. Luzi (1), F. Martinelli (1), B. Pace (3), A. Rovida (1), M. Taroni (1), F. Visini (1) and the MPS19 Working Group

(1) Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Rome, Italy (2) University of Naples, Federico II, Dept. Earth, Environmental, and Resources Sciences, Complesso di Monte Sant'Angelo, Via Cupa Nuova Cintia, 21, 80126 Napoli, Italy (3) DiSPUTer Department, Università Degli Studi Gabriele D’Annunzio, Chieti-Pescara, Italy

Abstract: We describe the main structure and outcomes of the new probabilistic seismic hazard model for Italy, MPS19 (Mappa di Pericolosità Sismica, 2019). Besides to outline the probabilistic framework adopted, the multitude of new data that have been made available after the preparation of the previous model MPS04, and the set of earthquake rate and ground motion models used, here we give particular emphasis to the main novelties of the modeling and the MPS19 outcomes. Specifically, we (i) introduce fault-based models, that use geological data to forecast earthquake occurrences, basing on long-term slip rates; (ii) use geodetic-models that, along with fault-based ones, furnish estimates of earthquake occurrences independent by the earthquake catalogue; (iii) introduce a novel approach to estimate and to visualize the epistemic uncertainty over the whole country; (iv) assign weights to each model components (earthquake rate and ground motion models) according to a quantitative testing phase and structured experts' elicitation sessions and; (v) test (retrospectively) extensively the MPS19 outcomes with the horizontal peak ground acceleration observed in the last decades, and the macroseismic intensities of the last centuries.

Keywords: PSHA

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Inferring seismic hazards from a new 1:25,000 scale map of active and potentially- active continental faults in Chile

Daniel Melnick (1, 2), Valentina Maldonado (1, 2), Martín Contreras (2), Julius Jara-Muñoz (3), Joaquín Cortés-Aranda (1, 4), Luis Astudillo (1, 4), José Miguel Martínez (1, 2), Andrés Tassara (1, 4), Manfred Strecker (3)

(1) Núcleo Milenio CYCLO (2) Universidad Austral de Chile (3) University of Potsdam (4) Universidad de Concepción

Abstract: Most of the seismic hazard along subduction zones is posed by great tsunamigenic earthquakes associated with the interplate megathrust fault. However, crustal faults are ubiquitous along overriding continental plates, some of which have been triggered during recent megathrust earthquakes. In Chile, the 2010 Maule earthquake (M8.8) triggered a shallow M7 earthquake on the fault, which had not been mapped and was unknown. In fact, M~7 earthquakes have recently occurred along unknown faults in California and , emphasizing the need for better and more detailed mapping initiatives. A first step towards a synoptic assessment of seismic hazards posed by continental faults at national level is mapping at a homogeneous scale to allow for a systematic comparison of faults and fault systems. Here, we present the first map of active and potentially-active faults in Chile at 1:25,000 scale, which includes published studies and newly-identified faults. All the published faults have been re-mapped using LiDAR and TanDEM-X topography, where available. Using different scaling relations, we estimate the seismic potential of all crustal faults in Chile. For specific faults where we have conducted paleoseismic and tectonic geomorphic field studies (e.g., Liquiñe-Ofqui, El Yolki, Mesamavida, and Pichilemu faults) we provide new estimates of slip rate, recurrence interval, and deformation style. We propose a segmentation model of continental faults systems in Chile, which are associated with distinct morphotectonic units and have predominant kinematics and relatively uniform slip rates. Using stress transfer models, we explore the potential feedbacks between upper-plate deformation and the megathrust seismic cycle.

Keywords: Potentially active faults, Chile

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Rupture History of the Himalayan Frontal Thrust in Central Nepal

Koji Okumura (1), Prakash Pokhrel (2), Hisao Kondo (3), Tomoru Yamanaka (1), Soma N. Sapkota (2)

(1) Hiroshima University, Higashihiroshima, Japan (2) Department of Mines and Geology, Kathmandu, Nepal (3) Geological Survey of Japan, AIST, Tsukuba, Japan

Abstract: The 2015 Golkha earthquake raised concern about the future large earthquake occurring in south of the 2015 source area. The 2015 earthquake ruptured 10 to 20 km deep portion of the plate boundary interface ~50 km away from the surface trace of the frontal thrust. It is necessary to evaluate the earthquake potential of the shallowest part of the Himalayan Frontal Thrust in central Nepal. After 5 years of intensive studies on the rupture history, now there are important questions about three large past earthquakes of 1934, 1344, and 1255 (or 13 century). They are, (1) the existence and extent of 1934 surface rupture, (2) the existence and extent of 1344 rupture, and (3) the extent and exact timing of 1255 (or 13th century) event. As to the 1934 surface rupture, Rizza et al. (2019) as well as Sapkota et al. (2012) demonstrated ruptures on fault exposures against Wesnousky et al. (2018) in Bardibas area. However, the west ternmination of the 1934 rupture has not been defined yet. We excavated two trenches near Bagmati River to examine the termination and to know the rupture history. We have successfully identified 1344 event in a trench near Butwal at the westernmost central Nepal. In our trench in west of Butwal, there was no evidence 1255 and 1505 ruptures but that of the 1344 rupture. This result confirms the existence of 1344 earthquake on the western central part of the frontal thrust and the terminations of 1505 and 1255 ruptures respectively in west and in east of Butwal. Our trenches near Bagmati River exposed multiple events. The dating of the events will define the extent of 1934, 1344, and 1255 ruptures.

Keywords: Rupture history, Himalayan frontal thrust, Nepal

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Recording the giant 1877 CE tsunamigenic earthquake and its predecessors from submarine laminated sediments off Northern Chile (19°35’S)

Cristina Ortega (1,2)*, Gabriel Easton (2), Tomás de la Fuente (2), Sofía Rebolledo(2)

(1) Departamento de Geología, Facultad de Ingeniería y Arquitectura, Universidad Central de Chile, Santa Isabel 1186, Santiago, Chile (2) Departamento de Geología, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Plaza Ercilla 803, Santiago, Chile *corresponding author e-mail: [email protected]

Abstract: The subduction margin of the Nazca plate beneath the South American plate along Northern Chile is considered among the major seismic gap worldwide. No mega-earthquake has happened along the hyperarid margin of Northern Chile since the last Mw~8.6-8.8 1877 CE historic event that generated a large Mt 9.0 tsunami. Considering the scarce chronicles in this region, it is imperative to assess the occurrence of past giant earthquakes based on high resolution geological records. Marine sediment cores and surface sediments from Pisagua bay (19°35’S) give us the opportunity to perform paleoseismological estimations in the Northern Chile seismic gap. Slumps and deformed sediments of centimetric scale (3 to 10 cm) interbedded among horizontal laminae can be taken as evidence of up to nine units, eventually generated by subduction earthquakes, that preceded the occurrence of 17cm thickness homogenite unit, most probably related to the 1877 CE episode. Furthermore, three centimeters of deformed laminae observed at the top of the marine core would be associated to the recent earthquake Mw 8.1 occurred off Iquique-Pisagua in 2014. Based on the thickness and the sedimentary structures of the marine record of Pisagua bay, and considering the gentle bottom slope, we propose that the homogenite was caused by the giant 1877 CE tsunamigenic earthquake, and that the underlying units were generated by previous earthquakes that caused similar effects in the Pisagua bay. Further studies are needed to better constrain these paleoseismological estimations.

Keywords: Mega-earthquake, Pisagua, marine sediment, Northern Chile

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Outreach on Earthquake Geology as a tool to increase social seismic awareness

M. Ortuño (1), E. Masana (1), R Pallàs (1), M. Ferrater (2), J. Bordonau (1)

(1) 1RISKNAT Group, Geomodels Institut. Facultat de Ciències de la Terra, Universitat de Barcelona, 08028 Barcelona, Spain ([email protected]) (2) Secondary School Manuel de Cabanyes, Av. Francesc Macià 110-114, Vilanova i la Geltrú, Barcelona, Spain.

Abstract: One of the factors that hinders the social identification of seismic risk in regions of moderate and slow deformation is the large time span since the last destructive event. We propose to strengthen the use of outreach tools in Earthquake Geology to attract the attention of population towards the exposure to seismic risk, especially among children and youngsters. Three main lines of action are explored; 1) a teacher’s guide (for primary and secondary courses) to the short documentary on earthquake geology “Earthquake land”, which presents two modalities: one designed to be used for teachers who may not have a background on earth sciences and want to use it as teaching tool on prevention and another devoted to acquire basic knowledge on earthquake geology, being both adaptable to different levels; 2) a web page compiling concepts, definitions and links on earthquake geology, with special focus, in this first stage, on the ; 3) a number of practical activities proposed to document the seismic landscape that surrounds us, both natural and architectural, which can be used in schools, community colleges, city hall prevention actions, etc. This third line assumes that awareness of the exposure to earthquake damaging effects can be increased through participative strategies promoting the search of the record of the “seismic past”. This can be achieved by identifying the imprints of past earthquakes (architectural/cultural heritage and the living memory) in the buildings but also in the natural landscape’s surroundings of their towns. We provide some examples of how these strategies are already being implemented at different localities in Spain and recall the need to generate an inclusive and living discourse, by incorporating the proposals and suggestions of young participants (subjects of the experiences), which go from passive recipients to primary actors of the prevention strategy.

Keywords: Earthquakes, Social impact, Education

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Surface rupturing earthquake in the Lower Rhine Grabens: results from paleoseismological trenching – “one shot faults”?

Osthof, Johanne (1), Reicherter, Klaus (1), Connotte, Frederic (1), Keller, Moritz (1), Menz, Alexander (1), Wirbs, Chris (1) and Hürtgen, Jochen (1)

(1) Inst. for Neotectonics and Natural Hazards, Lochnerstr. 4-20, 52056 Aachen, Germany, email: [email protected]

Abstract: The Rhine Graben system in Central Europe is seismically active, and hosts a set of major faults. We present preliminary results on the western boundary fault of the Lower Rhine Graben (LRG) based on geophysics and paleoseismology. The LRG is one of the most seismically active areas in the stable continental interiors of Central Europe. The most prominent historical earthquake is the Düren 02/18/1756 earthquake with Mw 6.2-6.7. In addition, damaging earthquakes in the westernmost part of the graben occurred near Aachen in 803/829, 1881, Herzogenrath in 1873 and 1878, Verviers in 1692, and Roermond in 1992, but the Düren and Verviers are regarded as strongest events. Following morphotectonic and geophysical investigations, we studied long trenches of pipeline construction in the LRG with several parallel fault strands are marked by topographic steps, by varying hydrogeologic condition and by geophysical anomalies in the subsurface (GPR and ERT data). Trenches crossed several topographic scarps of the Sandgewand and Birkesdorfer Fault (active branches of the Rurrand Fault). Paleoseismological trenches across the Birkesdorfer Fault in the Düren area revealed indications of young surface rupturing earthquake(s). The vertical displacement is on the order of 0.2–0.4 m along a major escarpment, and has been dated by radiocarbon to around 250 years (Düren 1756 event?). Sedimentary architecture and GPR data suggest the occurrence of several stepped faults that we interpret as a basin-ward “younging” of extensional normal faults. The Sandgewand Fault is one of the major faults of the area (ca. 23 km long, estimated magnitude ~6.3). Geophysical data and trenching have been used to map the fault and estimate its activity. The fault did not rupture during 1756, but has several surface rupturing events before. Those are clustered and concentrated around the early Holocene, possibly as post-glacial events.

Keywords: Intraplate earthquake, Europe, normal faults, paleoseismicity

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Quaternary deformation along the Western Andean Front (WAF) between 35° and 37° S, Chile: insights from morphometric analysis

J.A. Oviedo Reyes (1), J. Cortes-Aranda (1,2), A. Tassara (1,2), D. Melnick (2); Fernández (1)

(1) Universidad de Concepción (2) Millennium Nucleus the Seismic Cycle along Subduction Zones, Cyclo.

Abstract: The Western Andean Front (WAF) is the longitudinal border between the Central Valley (CV) and the Main Cordillera (MC) along the Chilean Andes. At different latitudes between 18°S and 34°S, this border has been described as controlled by west-vergent folds and thrusts. At 34°S, eastwards Santiago, the Quaternary activity of the WAF manifests in the occurrence of 3 to >100 m height scarps built in the flanking the MC. Up to date, the Quaternary activity of the WAF further south remains unknown. Herein, we present preliminary morphometric data to qualitatively assess the level of Quaternary activity along the WAF between 35°S and 37°S. We employed an AsterDEM 30m to map the main basins draining the WAF in the area and compute the following indices: hypsometric Integral (IH), elongation Ratios (Re), Asymmetry Factor (Af), mountain front Sinuosity (Smf), stream profile Morphometry (Cmax, Cf) and statistical moments of the hypsometric curve: skewness (Sk), Kurtosis(Dsk), Density Skewness(Dsk) and Density Kurtosis (Dkur). Additionally, we use the Swath Profiles some selected sites to describe the principal topographic changes and relationships with local relief to enhance morphometric indices analyses. The obtained data suggest low to moderate uplift rates along different segments of WAF in the studied area. Interestingly, one of the most active segments is the one located at ˜36°S, where a Holocene scarp has been built in alluvial deposits by the formerly defined Mesamávida Fault. Ongoing work is intended to refine the morphometric analysis and determine the relative level of tectonic activity (RTA) for the WAF segments between 35°S and 37°S. Since paleoseismic surveys have demonstrated that this structure is seismogenic at 34°S (the San Ramón Fault), the determination of the RTA is a crucial step for assessing the seismic hazard at which important cities and critical facilities between 35°S and 37°S are subjected.

Keywords: Quaternary deformation, Western Andean Front, central Chile

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Speleoseismology as a tool to validate and constrain seismic hazard models: examples from Central and Southern Apennines in Italy.

Bruno Pace (1), Luigi Ferranti (2) Alessandro Valentini (3)

(1) Università degli studi “Gabriele d’Annunzio”, Chieti-Pescara, Italy (2) DiSTAR - Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse Università di Napoli "Federico II”, Italy (3) International Atomic Energy Agency, Austria

Abstract: In the last thirty years, speleothems have become excellent tools for paleoenvironmental and paleoclimatic reconstructions of the Quaternary. Recently, in addition to these kinds of studies, an important scientific application regards speleoseismological reconstructions. In particular, it has been argued that natural speleothems could give important constraints on seismic hazard estimates since they have survived all the earthquakes over their life span. The underlying idea is based on the stalactite-stalagmite oscillatory system, which represents the vertical datum. The deviation of the growth axis from the vertical, and the speleothem breakage, could be evidence for shaking of the cave walls, excluding the possibility of other of deformation sources (landslide, flooding, ice flow, animal or anthropic passage). However, the difficulty in quantitative modelling of the observed deformation, and its direct attribution to a seismogenic source remains a major issue. In this work we present speleoseismological studies carried out in the Pollino Range (Calabria, southern Italy) and in Central Apennines (Abruzzo, central Italy), where we used the speleothems data to validate and improve the seismogenic sources models and the fault-based probabilistic seismic hazard estimates. In the first case- study the results highlight that a speleoseismological approach can be fruitfully applied in regions with low active tectonic rates and with caves where both the record of speleoseismic events and fragile intact speleothems are present. In the second case-study, the collapse of a massive speleothem permitted to establish whether this collapse can be considered as the record of a large paleoearthquake occurred in the past, and a fault-based seismic hazard model together with a numerical modelling allowed to define the possible source responsible of the collapse. Because on‐fault trenching is not always possible, the proposed approaches integrate information on activity for faults in various tectonic context.

Keywords: Speleoseismology, Seismic Hazard, Active Tectonics, Apennines

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Morpho structural and Paleo-seismological analysis of the Pachatusan Fault System – Cusco, Peru

A. Palomin (1), C. Benavente (1), L. Rossel (1), B. Garcia (1), E. Aguirre (1), S. Zerathe (2) and L. Audin (2)

(1) Instituto Geológico, Minero y Metalúrgico INGEMMET, San Borja, Perú (2) Université Grenoble Alpes, CNRS, IRD, ISTerre, 38000 Grenoble, France

Abstract: The Pachatusan Fault System (PFS) locates in Eastern Cordillera Peru, ~3 km northeast to Cusco. It consists of several lineaments of pluri-kilometric extension mainly trending NW-SE. The PFS has clear morphological signatures in the landscapes. It affects volcanic deposits (0.5 Ma), Holocene moraines and other LGM glacial morphologies thus attesting its recent tectonic activity. We carried out morpho-structural mapping of the faults using high resolution images (5 cm/px to 2 m/px), added to extensive field work, paleo seismological investigation and 14C dating. The morpho structural analysis of 201 swath profiles evidences tectonic structures associated with an active faulting. We describe a continuous NW–SE faults with a total of 28.5 m cumulated vertical offset and a sinestral lateral displacement of 16.9 m. These cumulated offsets affect geomorphic markers of the last glacial maximum (~14ka). Therefore, the Pachatusan faults zone can thus be described as a normal NW – SE faults system with left lateral component. A total of 99 km of cumulated fault scarps were mapped in high detail, distributed along 25 km in a width of 2 km. Subsequently, we excavate a trench of 8 m long and 3 m deep along an offsetted fluvioglacial deposit. We interpret 4 reactivations of the main fault segment since the last 4 ka years, with intervals of recurrence of ~1 ka. Interestingly, the last reactivation which generated a vertical displacement of 10 cm of a lacustrine level occurred between 1876 and 1948. Such timing corresponds to the local 1950 earthquake, a Mw6 that affected the city of Cusco and caused serious damages. Finally, older events identified along the trench may open new perspectives in our understanding of the Inca civilization resilience against the seismic hazard.

Keywords: Active fault, paleo seismology, morpho structural

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Slow-slip active faults in tropical areas: the case of the Opak Fault System (Central Java, Indonesia)

Sara Pena-Castellnou* (1), Natalie Drießen (1), Vanessa Steinritz (1), Gayatri Indah Marliyani (2), Klaus Reicherter (1)

(1) Neotectonics and Natural Hazards – Neotektonik und Georisiken, RWTH Aachen University, Aachen, Germany. * [email protected] (2) Geological Engineering Department, Universitas Gadjah Mada, Yogyakarta, Indonesia.

Abstract: Tropical areas often lack neotectonic studies as a result of several processes such as deep-weathering, thick vegetation covers, thick tropical soil, and high erosion rates among others that may cover faults and erase its related geomorphology. The island of Java forms part of the volcanic arc resulting from the subduction of the Australian Plate beneath the Sunda Plate. Subduction controls the current stress field of Java leading to a north-south maximum stress direction, which has generated E-W trending thrust belts and re-activated SW-NE structures as slow strike-slip faults that accommodate the tectonic strain generated by the deeper subduction mechanism within the volcanic arc. These shallow slow-slip faults are characterized by a poor surface geomorphological expression, long earthquake recurrence intervals and, often a very short seismic catalogue. Our work focuses on the Opak Fault System which has a clear NE-SW striking topographic expression located in the vicinity of the densely populated city of Yogyakarta (>4 M people). This area came into focus after the 27th of May 2006 Mw 6.3 earthquake that caused more than 6000 fatalities and a $3 billion economic loss. To this day, the causative fault of this earthquake remains uncertain. We carried out an analysis of morphometric parameters (normalized channel steepness index, knickpoint distribution, drainage basin asymmetry, and hypsometric integral) utilizing the DEMNAS elevation model, supported by geomorphological and structural field data to define the geometry, kinematics, and activity of the Opak Fault System. This methodology has proved to be a valuable tool in this kind of environment. We present up to date the most complete fault map of the area that will contribute to seismic hazard assessment.

Keywords: Opak Fault, Java, Tectonic Geomorphology, Active Tectonics

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Radon (222Rn) soil exhalation of the Alhama de Murcia fault and earthquakes.

R. Pérez-López (1), C. Guardiola-Albert (1), J.J. Martínez-Díaz (2), M. Bejar-Pizarro (1), A. Staller (3), A. Sanchez-Malo (4), Enrique Sanz (4), A. Fernández-Cortes (5), J.M. Calaforra (5)

(1) Geological Survey of Spain. IGME C/Ríos Rosas 23, Madrid 28003. SPAIN. [email protected], [email protected], [email protected] (2) Dpto. de Geodinámica, Estratigrafía y Paleontología, Universidad Complutense de Madrid. 28040, Madrid. [email protected] (3) Dpto. de Ingeniería Topográfica y Cartografía. ETSI en Topografía, Geodesia y Cartografía. Ctra. Valencia km. 7. Campus Sur. Universidad Politécnica de Madrid. 28031-Madrid. [email protected] (4) GEOMNIA NATURAL RESOURCES S.L. [email protected] (5) University of Almeria, Research group Water Resources and Environmental Geology, Spain. [email protected] , [email protected]

Abstract: We have used the soil radon emission for characterizing different tectonic segments of the fault of Alhama de Murcia (FAM, SE of Spain), one of the most active on-shore tectonic faults in Spain. The FAM is a strike-slip fault with a reverse component and NE-SW striking. The fault surface trace is about 90 km and shows paleoseismic evidence that suggests paleoearthquakes of size M 7. The last destructive earthquake of the FAM took place in the village of Lorca 2011 (Mw 5.2) and killed 9 people. Tectonic segmentation of this fault has been proposed, with a tectonic slip-rate close to 0.1 mm/yr from geomorphic evidence, whereas 0.5 mm/yr. has been suggested from GPS geodetic measurements. Mobilization of radon gas (222Rn) in tectonic areas is related to CO2 emission, acting as a gas carrier from deep fractured zones. The fluctuation of radon soil exhalation could be correlated with earthquake occurrence in the nearby. We have carried out a one-year comprehensive study of radon soil exhalation on the whole FAM surface trace by 50 small drills (0.8 m depth) from west to east. We have introduced radon passive detectors equipped with LR115 films in rambla deposits, deposits which were affected by the recent fault movement. We assume equivalent permeability conditions for radon transport by the FAM in the point of measuring. The passive detectors are closed housings type DRF, with a filter that avoids thoron disturbance. Results show the largest values of radon emission close to the Quaternary surface ruptures (ca 7.5 kBq/m3). The Lorca segment shows 13 an anomalous carbon isotopic composition of CO2 from air content in the Quaternary rambla deposits ( dCO2 = -7.24‰), which indicates that this residual gas (with a concentration of roughly 0.15%) is a mantle-rootled CO2, i.e. non-soil derived CO2 flux. This fact corroborates that the FAM exhibits permeability from the lower limit of the upper crust in this area. The one-year analysis has been divided into three-month experiments (four different maps) of soil exhalation, and geostatistical analysis was carried out to map the radon emissions. In addition, we have mapped also the seismic energy released related to shallow earthquakes (depth < 15 km), overlapping the fault trace at a maximum distance of 10 km. These results are part of the combined Spanish projects TRIGEO (CGL2017-83931-C3-2-P) and GEIs-SUB (CGL2016- 78318-C2-1-R and CGL2016-78318- C2-2-R).

Keywords: Radon, earthquakes, carbon dioxide, fault, Spain

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Speleoseismology at Los Casares Cave (central Sapin): evidence of a paleoearthquake?

R. Pérez-López (1), M. Á. Rodríguez-Pascua (1), P. G. Silva (2), L. Luque (3), M. A. Perucha-Atienza (1), J. Elez (2), J. L. Giner-Robles (4), E. Roquero (5) M. Alcaraz-Castaño (3) and J. Alcolea-González (3)

(1) Geological Survey of Spain. IGME C/Ríos Rosas 23, Madrid 28003. SPAIN. [email protected], [email protected], [email protected] (2) Dpto. Geología Universidad Salamanca, Escuela Politécnica Superior de Ávila. [email protected] ;[email protected] (3) Área de Prehistoria, Universidad de Alcalá de Henares. C/ Colegios 2, 28801 Alcalá de Henares. [email protected], [email protected] (4) Facultad de Ciencias. Universidad Autónoma de Madrid. [email protected] (5) Dpto. Edafología. E.T.S.I. Agrónomos. Universidad Politécnica de Madrid. [email protected]

Abstract: Los Casares Cave (Riba de Saelices, Guadalajara) represents an excellent Middle Palaeolithic archaeological site with evidence of Neanderthal –Sapiens different occupational stages (ca. 45±3 ka BP, Alcaraz-Castaño et al., 2017). Despite of the small spatial development of the karstic system (250 m length of main gallery and E-W trending), a destruction layer was recognized affecting the speleothems of a small hanging gallery. Different apparently coetaneous soda-straws, stalactites and stalagmites were broken, tilted and displaced. The location of the destruction horizon is placed out of the reach from any possible anthropological manipulation, in a hanging roof 6 meters high. We have carried out a systematic measurement of broken soda-straws and samples were collected to be analysed by using Uranium series. Also, tilting and stalagmite displacement were measured. Despite of, no data is available about numerical dating so far. Preliminary results from the cave destruction level and fallen blocks located outside the cave, suggest the occurrence of a paleoearthquake either from far-field seismic source (> 50 km) of estimated magnitude M > 6, or from a near-field seismic source (< 10 km), and with magnitude 4.5

Keywords: Cave, paleoearthquake, Palaeolithic, stalagmite, Spain

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Pleistocene earthquakes in the Southern Peribalticum area - the GREBAL project summary

Małgorzata Pisarska-Jamroży (1), GREBAL team

(1) Institute of Geology, Adam Mickiewicz University, Poznań, Poland; e-mail: [email protected]

Abstract: Sedimentological traces of earthquakes (seismites) within Pleistocene sediments linked mainly to glacio-isostatic adjustment (GIA) caused by loading/unloading of Scandinavian Ice Sheet were objectives of the GREBAL project. Studies were conducted during last four years in the northern part of Germany, Poland, Lithuania, Latvia and Estonia (so called the Southern Peribalticum area). The investigations consists of sedimentological analysis (logging, lithofacies analysis, grain size analysis, structural measurements and analysis), microstructural analysis, collection of samples for OSL datings and acquiring of absolute geochronological data, numerical analysis of glaciation-induced stress state changes and its implications for GIA-induced earthquakes. We found seismites (seismite=layer deformed as a result of seismic activity) in ten study sites in glaciolacustrine/lacustrine and fine-grained fluvial sediments of Pleistocene-age (three study sites in Poland, one study site in Germany, two study sites in Lithuania, one study site in Estonia, and three study sites in Latvia). Seismic activity did accompany Saalian and Weichselian glaciations and occurred in different periods of glacial cycle - during or after deglaciation and during ice-advance periods. Earthquakes caused by the reactivation of pre-Quaternary faults due to stress state changes were the most probable source of interpreted seismic activity. However, glacial earthquakes caused e.g. by large-scale, violent stick-slip motion are also discussed as probable source of seismic activity. Moreover, we made a kind of inventory of evidences of structural and textural features that could help in distinction of the soft-sediment deformation structures formed as a result of the shock waves propagation from those that arise as a result of other processes related to glacial and periglacial processes. The study has been financially supported by a grant for the GREBAL project (No. 2015/19/B/ST10/ 00661) from the National Science Centre Poland.

Keywords: Seismites, liquefaction, earthquakes

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Evidence of Holocene Subduction Earthquakes on the Central Hikurangi Subduction Margin

Charlotte Pizer (1), Jamie Howarth (1), Kate Clark (2)

(1) School of Geography, Environment and Earth Sciences, University of Wellington, PO Box 600, Wellington, 6140, New Zealand [email protected] (2) GNS Science, Fairway Drive, Avalon 5010, PO Box 30-368, Lower Hutt 5040, New Zealand

Abstract: Palaeoseismology offers a powerful tool to extract evidence of prehistoric subduction earthquakes on millennial timescales. This is necessary in locations such as the Hikurangi subduction margin in New Zealand, where full seismic cycles have not been observed in historic times. At the boundary between the central and southern sections of the margin, a transition from strong to weak interseismic coupling is accompanied by changes in several plate interface characteristics, but the influence that these present-day geophysical properties have on large earthquakes is poorly understood. Investigating the palaeoseismology of the two sections is useful for understanding the long-term patterns of earthquake behaviour and possible relationships between rupture zones and subduction interface properties. The longest subduction earthquake record for the entire subduction zone is from the central margin (Mahia to Cape Turnagain). Paleoelevation analysis of the former tidal inlet of Ahuriri Lagoon in Hawke’s Bay, provides evidence of 10 large earthquakes that have accumulated 8-9 m of mid- to late Holocene tectonic subsidence (Hayward et al., 2016). Lithological unconformities mean that each core rarely contains more than four events, resulting in a range in strength of evidence for earthquake ages and poor age control on certain earthquakes. Preliminary dating of submerged paleosol sequences in the Pakuratahi Valley (15 km north) have presented contrasting chronologies, calling for further studies to clarify the timing of subduction earthquakes in the region (Clark et al., 2019). Although the tsunami hazard presented by subduction earthquakes in Hawke’s Bay is well known (Goff, 2008; Wallace et al., 2014), the identification of paleotsunami evidence has not been central to recent work, presenting an additional gap in current knowledge for the central margin. This study revisits the Pakuratahi Valley and other nearby coastal wetlands to obtain evidence of both vertical land deformation and tsunami inundation related to large Holocene subduction earthquakes with an emphasis on high-resolution chronologies. In addition to this, we aim to combine the onshore evidence with new offshore evidence paleoearthquakes from turbidites within offshore sediment cores.

Keywords: Holocene subduction earthquakes, Central Hikurangi subduction margin

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Sand deposits reveal great earthquakes and tsunamis at Mexican Pacific Coast

María-Teresa Ramírez-Herrera(1), Néstor Corona(2), Jan Cerny(1), Rocío Castillo-Aja(3), Diego Melgar(4), Marcelo Lagos(5), Avto Goguitchaichvili(6), María Luisa Machain(7).

(1) Laboratorio de Tsunamis y Paleosismología, Instituto de Geografía, Universidad Nacional Autónoma de México, México. [email protected], [email protected] (2) COLMICH, Centro de estudios de Geografía Humana, Michoacán, México; and Laboratorio de Tsunamis y Paleosismología, UNAM. (3) Depto. de Geografía y Ord. Territorial, CUCSH. Universidad de Guadalajara, México (4) Department of Earth Sciences, University of Oregon, Oregon, USA. (5) Instituto de Geografía, Laboratorio de Tsunamis, Pontificia Universidad Católica de Chile, Santiago, Chile (6) Instituto de Geofísica, Universidad Nacional Autónoma de México, Unidad Michoacán, México (7) Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, México

Abstract: Globally, instrumentally based assessments of tsunamigenic potential of subduction zones have underestimated the magnitude and frequency of great events because of their short time record. Historical and sediment records of large earthquakes and tsunamis have expanded the temporal data and estimated size of these events. Instrumental records suggests that the Mexican Subduction earthquakes produce relatively small tsunamis, however historical records and now geologic evidence suggest that great earthquakes and tsunamis have whipped the Pacific coast of Mexico in the past. The sediment marks of centuries old-tsunamis validate historical records and indicate that large tsunamigenic earthquakes have shaken the Guerrero-Oaxaca region in southern Mexico and had an impact on a bigger stretch of the coast than previously suspected. We present the first geologic evidence of a great tsunamigenic earthquake near the trench of a subduction zone previously underestimated as potential source for great earthquakes and tsunamis. Two sandy tsunami deposits extend over 1.5 km inland of the coast. The youngest tsunami deposit is associated with the 1787 great earthquake, M 8.6, producing a giant tsunami that poured over the coast flooding 500 km alongshore the Mexican Pacific coast and up to 6 km inland. The oldest event from a less historically documented event occurred in 1537. The 1787 earthquake, and tsunami and a probable predecessor in 1537, suggest a plausible recurrence interval of 250 years. We proved that the common believe that great tsunamis do not occur on the Mexican Pacific coast cannot be sustained.

Keywords: Tsunami, earthquake, subduction, historic and geologic evidence, Mexican Pacific coast

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Surface rupturing earthquake in the Upper Rhine Grabens: results from paleoseismological trenching

Reicherter, Klaus (1), Sara Pena-Castellnou (1), Hürtgen, Jochen (1), Stephane Baize (2) and Joachim Ritter (3)

(1) Inst. for Neotectonics and Natural Hazards, Lochnerstr. 4-20, 52056 Aachen, Germany. [email protected] (2) IRSN, France, [email protected] (3) KIT, Univ. of Karlsruhe, Geophysical Institute, Germany, [email protected]

Abstract: The Rhine Graben system in Central Europe is seismically active, and hosts a set of major faults. We present preliminary results and interpretations on the eastern central boundary fault of the Upper Rhine Graben (URG) based on geophysics and paleoseismology. The URG is one of the most seismically active areas in the stable continental interiors of Central Europe north of the Alps. The most prominent historical earthquake is the Basel 10/18/1356 earthquake with Mw 6.7-7.1, that is thought to have produced surface rupture. In addition, historical damaging earthquakes farther N of Basel in the central part of the graben occurred near Kappel- Grafenhausen in 1728, Rastatt in 1737 and 1933, Rheinstetten in 1948, and Seltz in 1952. After extensive morphotectonic and shallow geophysical investigations and analyses, we discovered that the eastern central Rhine Graben Boundary Fault (RGBF) consists of several parallel fault strands that are marked by topographic steps, by varying hydrogeologic conditions (moisture content) and by geophysical anomalies in the subsurface (GPR and ERT data). We opened six paleoseismological trenches in the Ettlingen area (south of Karlsruhe) and discovered indications of surface rupturing earthquakes. The cumulative vertical displacement is on the order of 0.6 – 1 m, and there is considerable horizontal offset of ca. 2 m. Sedimentary architecture suggest the occurrence of three distinct events that we interpret as on-fault effect of earthquakes with magnitude > 6. Radiocarbon dating and OSL dating is used to dated and bracket the events, that all occurred before c. 2000 years, possibly in a cluster in the earliest Holocene after the LGM. Our findings contribute significantly to the completeness of the earthquake history in the URG what is important concerning modern seismic hazard assessment. Further studies, regarding segmentation of the very long fault, activity of different strands and recurrences periods, need to be addressed.

Keywords: Intraplate earthquake, Europe, strike-slip faults, paleoseismicity

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Active faults or weakness zones in the northern Chile forearc? Understanding the competition between subduction earthquake cycle and upper plate fault reactivation in subduction zones

Gabriel González (1,2), Eric Jensen (1,2), Mahesh Shrivastava (1,2), Paulina Rivera (1), Yerko González (1)

(1) Departamento de Ciencias Geológicas, Universidad Católica del Norte, Avenida Angamos 0610, Antofagasta Chile. (2) National Research Center for Integrated Natural Disaster Management (CIGIDEN), Vicuña Mackenna 4860, Santiago, Chile.

Abstract: The Atacama fault system in northern Chile consist of several branches containing reactivated normal fault segments expressed by the occurrence of fault-scarps along kilometer-scale surface ruptures. Optical luminescence reported that these faults were formed during Pleistocene (< 40 ky before Present) and Holocene. However, geodetic data from permanent GPS stations located in the Coastal Range of northern Chile shows that there is no evidence of elastic strain accumulation across major upper-plate faults, i.e. the earthquake generation in these faults not follows a typical behavior according to the earthquake cycle. Another observation is that the fault lengths are generally shorter than the surface displacements and this is not scaled with the proposed in the literature. Are really these faults “active faults” or weakness zones? To solve this problem, it is proposed a research methodology, which aims to unravel the main factors controlling the upper-plate faults reactivation in subduction settings. The methodology designed contemplates a combination of geological fieldwork, high-resolution satellite imagery inspection, trench mapping, petrographic and structural characterization of fault zones, mechanical tests of rock samples in laboratory and numerical modelling. The results of this research will be a key element to improve the seismic hazard assessment in subduction conditions, particularly in Chile, where the seismic risk related to upper-plate faults is poorly developed due to the scarcity of geological and geophysical data. This research will be financed by recently awarded FONDECYT project.

Keywords: Atacama Fault System, active faults, reactivation, weak faults.

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Rupture Complexity in Large Strike-Slip Earthquakes: Rule or Exception?

Thomas K. Rockwel (1) and Yann Klinger (2)

(1) Geological Sciences, San Diego State University, San Diego, CA 92182, [email protected] (2) Tectonics Lab, IPGP, France; [email protected]

Abstract: The rupture patterns of published plate boundary ruptures are compared to the ruptures of large earthquakes that occurred off of the main plate boundary faults. All of the well-documented complex strike-slip ruptures occurred on low slip rate faults with long recurrence intervals, whereas high slip rate plate boundary faults have produced relatively simple ruptures that tend to only involve the main fault zone. One factor they may contribute to this behavior is fault healing: long RI faults have much more time for healing and may be stronger than fast plate boundary faults with short RIs. Other factors may be fault roughness and maturity, as many of the low slip rate faults also have low total displacement. However, some of the low slip rate faults have accumulated substantial slip over a long period of time and would not qualify as “low slip”, making this explanation less favorable. In any case, the general idea that all ruptures are complex is not supported by the observations, and when considering off-fault damage and rupture, it seems apparent that there are at least two general classes of strike-slip faults - those with low slip rates that produce complex, multi-fault ruptures, and primary plate boundary faults with high slip rates that produce much simpler rupture patterns. Complexity in this context relates to the number of discrete faults that rupture in association with an earthquake main-shock. This model has implications for probabilistic fault displacement hazard analysis, as most slip will be much more localized on the main fault in question if that fault is a main plate boundary element. In contrast, much more off-fault damage may be expected on minor, secondary faults for larger earthquakes that nucleate on faults with long recurrence intervals.

Keywords: Rupture complexity, strike-slip earthquakes, plate boundary faults

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Paleoseismic Studies in Cusco: Evidence of paleo-earthquakes in the surface rupture zone of the 1986 earthquake

L. Rosell (1), C. Benavente (1), B. García (1), S. Wimpenny (2), R. Walker (3), Christoph Grützner (4), E. Aguirre (1), F. Delgado (5)

(1) Instituto Geológico, Minero y Metalúrgico INGEMMET, San Borja, Perú. [email protected] (2) COMET, Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Cambridge, UK (3) Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK (4) Institute of Geological Sciences, Friedrich Schiller University Jena, Jena 07749, Germany (5) Especialidad Ingeniería Geológica, Facultad de Ciencias e Ingeniería. Pontificia Universidad Católica del Perú, San Miguel, Lima 15088, Perú.

Abstract: In Peru there are historical and instrumental records of earthquakes in the last 500 years. These data come with limitations, but they can be complemented with paleoseismic records of past earthquakes. This would allow to identify the causative faults and to analyze their seismogenic capacity. So far it is poorly understood which faults ruptured in the known historical earthquakes. Therefore, these faults are not well understood in terms of average recurrence interval and maximum possible magnitudes. The city of Cusco is located next to a ~150 km-long active fault system. The Qoricocha fault, one of the segments of this system, is located 10 km north of the city. The fault ruptured in 1986 in an earthquake of Mb5.3, which had a ~3 km-long surface rupture despite its moderate magnitude. This event is one of the few historical examples of primary surface ruptures in the Andes. Therefore, the fault is an ideal starting point to better understand the seismic hazard of the region. Our study involves detailed mapping on high-resolution aerial images (0.25m/px), field surveys, paleoseismological studies, and radiocarbon ages. We show that the Qoricocha normal fault is expressed in the landscape by prominent ~16 km long, 0.10 to 6 m high scarps cutting Pleistocene volcanic rocks and Quaternary deposits. In addition, we present evidence for three earthquakes in the last 8700 yrs with magnitudes of Mw6.3-6.78. The slip rate of the fault is 0.08-0.17 mm/yr. Our results allow to affirm that the also minor segments that compose the Cusco Fault System are capable of generating large earthquakes. We observe that in addition to the Qoricocha segment, other smaller segments, such as the Tambomachay and Pachatusan faults, generated large earthquakes during the Holocene. This represents a significant hazard for the city of Cusco, which is a world tourist attraction with more than half a million of inhabitants..

Keywords: Surface rupture, Cusco, paleoearthquake

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Seismic Potential of Crustal Faults in the Chilean Andes

Isabel Santibáñez (1), José Cembrano (1), Carlos Costa (2) and Gabriel González (3)

(1) Departamento de Ingeniería Estructural y Geotécnica, Pontificia Universidad Católica de Chile. (2) Departamento de Geología, Universidad de San Luis, Argentina. (3) Centro de Investigación para la Gestión Integrada de Desastres, Departamento de Ciencias Geológicas Universidad Católica del Norte.

Abstract: Crustal faults in Chile, occurring in the overriding South American plate throughout the Andes, can be organized into three margin-parallel domains according to their spatial distribution from west to east: Outer Forearc; Inner Forearc; and Volcanic Arc. Faults lying on each of the margin-parallel domains share some first- order geometric and kinematic characteristics constraining their seismogenic potential. Current structural, paleoseismological, and geodetic data, although sparse and limited, show that slip rates of Chilean crustal faults range from 0.2 mm/y (in the forearc region) to up to ~10.0 mm/y (in the intra-arc region), with maximum hypocentral depths varying from 25–30 km depth in the outer forearc to 8–12 km depth in the volcanic arc. Faults in the outer forearc region have the potential to generate Mw 7 earthquakes every few thousand years. One key characteristic of these faults is that they can be reactivated as the result of Mw ~8.5+ subduction earthquakes (e.g. Pichilemu Fault in 2010, which generated two earthquakes only a few days after the Mw 8.8 Maule earthquake). However, earthquakes with Mw >7 can also occur since the cold, thick crust of the outer forearc region allows the nucleation of earthquakes with depths of up to 30 km. Typical faults from the inner forearc, such as the San Ramón Fault, have been shown to generate Mw ~7–7.5 earthquakes with similar or slightly longer recurrence times than typical faults of the outer forearc. Lastly, intra-arc faults, such as 40-km long segments of the Liquiñe–Ofqui Fault System in Southern Chile, are capable of producing Mw 6–7 earthquakes every few hundred years; however, their maximum size is limited by the relatively thin seismogenic crust (8–12 km), which prevents the propagation of earthquakes deeper down.

Keywords: Crustal Faults, Crustal earthquakes, Chilean Andes

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Locating Active (Holocene) Faults in the City of Beverly Hills, California (USA)

Roy J. Shlemon (1)

(1) Roy J. Shlemon & Assoc., Inc. PO Box 3066. Newport Beach, CA 92659-0620 – USA. [email protected]

Abstract: The Santa Monica fault zone (SMFZ) extends across much of the densely populated City of Beverly Hills in southern California. State and local agencies require that active (Holocene) splays of the SMFZ be located and avoided (structural setbacks) prior to new construction. Accordingly, based on interpretation of ~80-100 m deep continuous cores, on arrays of cone-penetrometer tests (CPT), on limited geophysical data, on local street trenching, and on downhole logging of up to 15-m deep, overlapping bucket-auger holes, the ~300- m wide SMFZ is now documented to impact at least several famous, multi-million-dollar commercial structures in the “heart” of the Beverly Hills business district (Rodeo Drive). Subsurface sediment correlation is typically based on initial interpretation on 3-m centered continuous cores and con penetrometer test soundings. However, local paleo-channel incision may be 0.5 to 1.0 m, inherently complicating lateral sediment correlation, especially when possible Holocene vertical displacement is less than a few cm. The depth to the local Pleistocene/Holocene boundary varies, but – based mainly on radiocarbon and soil-stratigraphic dating – locally occurs between ~ 6-8 m, typically too deep for urban trench exposure. Increasingly, therefore, consultants drill 20-30, overlapping, 0.8 m diameter bucket-auger holes, which, when cleaned and logged, emulate trench walls. Such drilling is particularly expensive in cities and is typically done at night to reduce disruption to traffic and commercial activities. Coupled with difficulties of locating and avoiding unmarked utility lines and with required State and City technical reviews and permits, investigating the possible presence and impact of active faults on a single Beverly Hills commercial building may take over a year and exceed a million US dollars.

Keywords: Urban active faults; investigation techniques; Beverly Hills, California

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Archeoseismological analysis of the late 4th century tsunami event devastating the Roman City of Baelo Claudia (Gibraltar Arc, South Spain).

P. G. Silva (1), J. Elez (1), P. Carrasco-García (2), G. Santos (2), J. Pérez-Tarruella (1), J. L. Giner-Robles (3), E. Roquero (4), K. Reicherter (5), I. García-Jiménez (6), F. Prados Martínez (7), R. Pérez-López (8), T. Bardají (9), M. A. Rodríguez-Pascua (8)

(1) Dpto. Geología Universidad Salamanca, Facultad Ciencias, 37008-Salamanca, Spain. [email protected] (2) Dpto. Ingeniería Cartográfica y del Terreno, Universidad Salamanca, 05003-Ávila, Spain (3) Dpto. Geología y Geoquímica, Facultad de Ciencias. Universidad Autónoma de Madrid, Madrid, Spain (4) Dpto. Edafología. E.T.S.I. Agrónomos. Universidad Politécnica de Madrid, Madrid, Spain (5) Neotectonics and Natural Hazards Institute. RWTH Aachen University, 52056-Aachen, Germany (6) Conjunto Arqueológico de Baelo Claudia. Área de Investigación y Conservación, Bolonia, Cádiz, Spain (7) Instituto. Univ. Investigación en Arqueología y Patrimonio Histórico, Universidad de Alicante, Spain (8) Instituto Geológico y Minero de España (IGME). Área Riesgos Geológicos. 28003-Madrid. Spain (9) Dpto. Geología, Geografía y Medio Ambiente; Universidad de Alcalá. 28805-Alcalá de Henares, Spain

Abstract: We report on the tsunami deposits burying the coastal roman remains of the Baelo Claudia archeologic site and its environs until ca. +8 m above the sea-level. New data on 2D ERT profiles (Electric resistivity Tomography) and GPR (Ground Penetrating Radar) the lagoonal zone near the eastern necropolis adjacent to the city walls as well as new sedimentologic insights on the paleotsunami deposits inside and outside the city are presented. The tsunami layer has been well documented inside the city in previous works and archaeologically dated in the late 4th century AD triggering the latter abandonment of the city. The tsunami layer is a dark cohesive sandy deposit (28 to 52 cm thick) containing fragments of pottery, fish and animal bones, glassware, bricks and large boulders of masonry blocks and column drums. The layer also contains microfaunal assemblages with a mixture of benthic and planktonic foraminifera as well as lagoonal brackish- water gastropods and numerous shell debris and broken reworked foraminifera. Data presented in this work indicate that the paleotsunami layer is mainly composed of well-rounded fine-medium sands originating from the reworking of aeolian and littoral beach deposits of the old roman spit-bar enclosing the ancient embayment. We interpret parts of the tsunami layer as backwash deposits trapped within the ruins of the city after the earthquake destruction. Recent findings in the eastern necropolis record a destroyed mausoleum of the late 2nd century in which the stratigraphy shows the earthquake destruction layer (with NE-SW collapsed marble columns), buried by the dark tsunami layer. The retrieved data indicate that the tsunami waves probably washed the ancient lagoonal area east to the city and the backwash debris go back WSW towards the city surpassing and partially destroying the eastern city walls. This interpretation can also explain the important amount of debris and rubbish incorporated to the tsunami layer, since the wave could mobilize part of the anomalous volume (ca. 1,500 m3) of waste accumulated against the outer side of the eastern city wall since the 2nd century. Within the city the N-S streets (cardos) directed the backwash deposits towards the sea, but the E-W ones (decumanus) acted as sediment traps. Research has been funded by the Spanish MINECO-FEDER Project QTECT-SPAIN (CGL2015-67169-P) and the Neotectonics and Natural Hazards Institute of the RWTH Aachen University (Germany)

Keywords: Archaeoseismology, tsunami deposits, dating, geophysical research, Cádiz, South Spain

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

The evolution of slopes in a seismically active carbonate terrain by normal faulting and generations of landslides, Galilee, Israel

Siman-Tov S. (1)

(1) Geological Survey of Israel, 32 Yesha'ayahu Leibowitz, Jerusalem, 9692100, Israel.

Abstract: Landslides are a type of mass wasting processes that endanger people and infrastructures around the globe. Nowadays, rockfalls are the most common type of landslides that occur in Israel and are triggered mainly by earthquake-induced ground motion or heavy rainstorms. In contrast, several geological and geomorphological observations have suggested that additional landslide types, e.g. slumps and debris avalanches, were active during the quaternary period in affecting hillslope evolution. In this study, we focus on the paleo-landslides that are common along the eastern part of the Zurim Escarpment, Galilee, Israel. A high- resolution digital surface model combined with aerial photos and field observations allow detailed mapping of the landslide scars and deposits. This map suggests that several generations of landslides shaped the slopes. We also conclude that in most cases, paleo-landslides are primarily controlled by the exposure of marl layers, along steep slopes that originated by normal faulting. Recently, the third dimension of this composite paleo-landslide structure was exposed in a 500 m long open channel, during road constructions. Cross-cutting relationships of the landslide deposits reveal the long history of landslide activity in this region. Along the channel walls, we observed highly deformed rock structures ranging from pulverized and folded layers to brecciated materials. The eastern part of the exposed channel contains the youngest landslide of the outcrop, which includes approximately one-meter thick vertisol layer that is sharply truncated by debris material composed of crushed limestone and marls. While exposing this highly localized sharp boundary, we found parallel slickensides that point to the southeast slip direction of the landslide. Recently, heavy rainstorms triggered some small slumps and larger debris slide along the channel, a close reminder to the potential hazardous of reactivation of paleo- landslides along the escarpment.

Key words: Normal faults, Carbonate terrain, Landslides

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Stress field changes in Central Europe since Late Miocene to date as determined from volcanic rocks and extensometric measurements in the Bohemian Massif, Central Europe

J. Stemberk jr. (1), M. Coubal (1,2), P. Štěpančíková (1)

(1) Institute of Rock Structure and Mechanics, The Czech Academy of Sciences, V Holešovičkách 94/41, Prague 8, 18000, Czech Republic. (2) Institute of Geology, The Czech Academy of Sciences, Rozvojová 269, Prague 6, 16000, Czech Republic.

Abstract: The presentation will show the results of the stress field reconstruction in area of the Rychlebské hory Mts. (Bohemian Massif, Central Europe) during period since Late Miocene to date and its implication to the fault kinematics and dynamics. The classical methods of paleostress were used and applicated on stria on slickensides datasets measured in the dated volcanic rocks and on present-day observed 3D fault movement dataset measured by extensometers - the TM-71 gauges. The results show switching of tectonic phases with dominant compression, transtension or extension. Each stress regime is characterized by the orientation of the principal parameters. Six different paleostress field regimes from the Late Miocene to Quaternary and three different to-date stress field regimes were distinguished. The timing of the derived regimes was determined more accurately in comparison with classical geological approach and is in good accordance with the data reported from different regions in western and northern European Alpine Foreland, which suggests their broader validity. The to-date stress field behaviour is characterized as non-linear, short-periodical switching of two compressional stress/strain states – WNW-ESE to NW-SE compression corresponding to the stress field of the Western European stress domain and NNE-SSW corresponding to the stress field of the NW part of the Carpathian stress domain. The extensional state, oriented NW-SE, corresponding to gravitational spreading due to the Rychlebské hory Mts. Quaternary uplift, was recognised. Moreover, the orientation of theoretical planes with maximum shear stress and with a high tendency to dilate for all individual (paleo)stress regimes were defined and compared with the orientation of known faults within the broader region suggesting their activity and kinematics.

Keywords: Central Europe, Bohemian Massif, Late Miocene-recent, stress field reconstruction

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Fault reactivation due to Ice Loading (Bohemian Massif, Central Europe)

Petra Štěpančíková (1), Thomas K. Rockwell (1,2), Jakub Stemberk (1), Filip Hartvich (1), Jozef Hók (4), Karen Luttrell (5), Madeline Myers (5,6), Daniel Nývlt (7), María Ortuño (8), Edward J. Rhodes ( 9, 10), Dylan H. Rood (11), Petr Tábořík (1,3), Neta Wechsler (12)

(1) Inst. of Rock Structure and Mechanics, Czech Acad. of Sci., Prague, Czech Rep. (2) Dept. of Geol. Sci., San Diego State Univ., California (3) Faculty of Science, Charles Univ., Prague, Czech Rep. (4) Faculty of Science, Comenius Univ., Bratislava, Slovakia (5) Dept. of Geology and Geophysics, Louisiana State Univ., Baton Rouge, Louisiana (6) Dept. of Geography and Planning, Queen’s University, Kingston, Ontario, Canada (7) Faculty of Science, Masaryk Univ., Brno, Czech Rep. (8) Risknat-Institute Geomodels, Dept. of Earth and Ocean Dynamics, University of Barcelona, Spain (9) Dept. of Geography, Univ. of Sheffield, S10 2TN UK (10) Dept. of Earth, Planetary and Space and Sciences, University of California Los Angeles, CA, USA (11) Dept. of Earth Science and Engineering, Royal School of Mines, Imperial College London, UK (12) Neev Center for Geoinfomatics, Fredy & Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerusalem, Israel

Abstract: We studied morphologically pronounced NW-SE trending Sudetic Marginal Fault (SMF), situated at the northeastern limit of the Bohemian Massif in central Europe. Eighteen paleoseismic trenches and thirty- four electric resistivity profiles were performed at the Bila Voda site to study the 3D distribution of a beheaded alluvial fan on the NE block of the fault. The estimate of left-lateral offset of the alluvial fan is 30 – 45 m from the source valley in the SE of the site. We used radiocarbon dating, OSL, IRSL, and 10Be cosmogenic dating to constraint the age of the fan, which varies from 20-70 ka with the full range of uncertainties. This gives us slip rates ranging from 1 to 4 mm/yr during late Pleistocene and 0 mm/yr during Holocene that was found already unfaulted. As the site lies ~150 km south from the Late Pleistocene Weichselian maximum (~20 ka) ice-sheet front, we hypothesized that the slip rate acceleration was due to ice-loading. Models of the related lithosphere flexure show that the failure on the SMF was promoted by the presence of the ice sheet, relative to an ice free state and that the most favorable time for a glacial-loading induced slip would be during the glacial maximum ~21-17 ka.

Keywords: Paleoseismic trenching, intraplate tectonics, Late Pleistocene faulting, ice-loading, Bohemian Massif

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Neotectonic deformations in a cave: constraints from Th/U dating of damaged speleothems (Demänová cave system, Low Tatra Mts, Western Carpathians)

Jacek Szczygieł(1), Michał Gradziński (2), Pavel Bella (3), Helena Hercman (4), Juraj Littva (3), Maciej Mendecki (1), Przemysław Sala(2), Wojciech Wróblewski (2)

(1) Institute of Earth Sciences, University of Silesia, Będzińska 60, 41-200 Sosnowiec, Poland (2) Institute of Geological Sciences, Jagiellonian University, Gronostajowa 3a, 30-387 Kraków, Poland (3) State Nature Conservancy of the Slovak Republic, Slovak Caves Administration, Hodžova 11, 031 01 Liptovský Mikuláš, Slovakia (4) Institute of Geological Sciences, Polish Academy of Sciences, Twarda 51/55, Warszawa, 00-818, Poland

Abstract: Damaged speleothems could be considered as an earthquake environmental effects (EEE) used in paleoseismology. Especially since speleothems are particularly effective for dating and caves have a great potential for preservation comparing to ground surface exposed to constant erosion. However, miscellaneous causes may result in similar deformations: ice creeping, freezing, compaction or liquefaction of deposits underlying speleothems, tectonics or just gravity movements. All those possible causes must be considered, which sometimes leaves more than one option. On the other hand, since many EEE such as liquefaction or landslides require M>5, in mid- and low-seismicity regions cave damage might be the only relicts of paleoseismic events. Such a region is the Central Western Carpathians, wherein the Demänová Cave System (Low Tatra Mts) several dozen broken, tilted and fractured speleothems were documented, some directly related to normal fault dislocated cave passage. Damaged speleothems samples were collected to determine the time interval in which the deformation took place by dating the youngest layer of the broken speleothem and the oldest layer of regrown one. In total 46 samples were taken in 28 sites. U-series dating allowed to determine at least three faulting events: 316.5 ± 4.8 – 291.8 ± 3.5 ka, 210 ± 2.3 – 84.5 ± 1.1 ka, and 66.7 ± 0.8 – 19.5 ± 0.2 ka. Considering that the valley has not been incised since at least 600 ka, relaxation as a trigger seems unlikely. Tectonic displacement along the fault appears to be the explanation. Such micro-dislocations were documented in other European caves. Yet, seismogenic or co-seismicity of the fault is difficult to determine due to the dating resolution and poor paleoseismic record in the Carpathian. The research project no. 2017/25/B/ST10/01430 is financed from the Polish National Science Center.

Keywords: U-series dating, Speleoseismology, Paleoseismology

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Coseismic paleo-displacements along the Mt. Vettore bedrock fault scarp revealed by high resolution topographic survey (central Italy, 2016 earthquake)

Testa (1), P. Boncio (1), M. Di Donato (1), G. Mataloni (2), D. Palumbo (2), L. Le Donne (2)

(1) CRUST-DISPUTer, Università “G. d’Annunzio” di Chieti-Pescara, Chieti, Italy. (2) Dipartimento di Architettura, Università “G. d’Annunzio” di Chieti-Pescara, Pescara, Italy.

Abstract: The 2016 central Italy earthquake (Mw 6.5) ruptured about 30 km of the Mt. Vettore - Mt. Bove normal fault. Maximum displacement of 2.4 m occurred at the base of a prominent limestone fault scarp. In order to analyse the features of the fault scarp in the area of maximum displacement, high resolution Terrestrial Laser Scanner (TLS) has been used. Nine different scans have been acquired. TLS data were integrated with photogrammetric survey. The survey allowed us to obtain a 4 ± 2 mm resolution 3D point cloud and to reconstruct a model of the basal fault scarp. Because of the long range of TLS, in some locations it was possible to obtain also a model of the entire long-term fault scarp (likely post-Last Glacial Maximum; i.e., 15 ± 3 ka BP). Four different generations of coseismic scarps were recognised and measured on serial profiles along the point cloud. From the bottom, the first one is the 2016 earthquake free face. The second one has a height comparable to the first one. The third scarp has not been detected on all the profiles. The fourth scarp’s height is comparable with the second one, so the second last and the fourth last earthquakes may have been similar. A comparison between the recognized scarps and the paleoseismological ages of past surface faulting earthquakes available in the literature for the same fault system, allowed us to correlate the second scarp to an event occurred about 1600 yrs BP, the third to an earthquakes occurred about 3000 yrs BP, and the fourth to an event occurred about 6500 yrs BP. The comparison between coseismic scarps and paleoearthquakes allowed us to obtain a slip rate of the order of 0.8 mm/yr (last 5-7 ka), with some speculations about fault slip behaviour.

Keywords: Paleoearthquake scarps, Terrestrial Laser Scanner, Photogrammetric survey

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Offshore tsunami backwash deposits - How to interpret palynological and micropalaeontological records?

Cristina Val-Peón* (1), Daniela Eichner (1), José A. López-Sáez (2), Lisa Feist (1), Klaus Reicherter (1), Pedro J.M. Costa (3) (4), Juan I. Santisteban6, Piero Bellanova (1) (5), Mike Frenken (1) (5), Ivana Bosnic (3) (5), Jan Schwarzbauer (5) and the M152 scientific team

(1) Neotectonics and Natural Hazards – Neotektonik und Georisiken, RWTH Aachen University, Germany. *[email protected] (2) Environmental Archaeology Research Group, Instituto de Historia (CCHS), C.S.I.C., Madrid, Spain (3) Instituto D. Luiz, Faculdade de Ciências, Universidade de Lisboa, Portugal (4) Earth Sciences Department, Faculty of Sciences and Technologies, University of Coimbra, Portugal (5) Laboratory for Organic-Geochemical Analysis, Institute of Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University, Germany (6) Department of Geodynamics, Stratigraphy and Paleontology, Fac. Geological Sciences, Complutense University of Madrid, Spain

Abstract: With the intention to study the sedimentological characteristics and the palaeoenvironmental effects of tsunami backwash deposits, the RV Meteor cruise M-152 recovered 19 sediment cores along two perpendicular transects in the continental shelf of the Algarve (Portugal). Some of them were analysed in a multi-proxy approach, revealing four potential event layers over the last 11 ka cal BP. High resolution palynological and micropalaeontological analyses were carried out on one of the western transect cores, GeoB23519-01. In addition, granulometry, magnetic susceptibility, P-wave velocities, organic, and inorganic geochemistry were analysed. The preliminary data allow drawing the palaeoenvironmental evolution along this time frame, with particular focus on the four event layers, of which one can be assigned to a tsunami event ca. 3700 cal BP and other to the AD 1755 Lisbon tsunami. Since palynomorphs are sensitive to be well preserved in sandy sediments, this core presents the chance for a better understanding about how palynological and micropalaeontological records can be used to study these kind of tsunami events. Interpreting biases provoked by pollen preservation is a major issue to discern the vegetation response to these infrequent high-energy events on off-shore deposits, and, therefore, to shed light into their impact in the on-shore landscape configuration.

Keywords: Palaeopalynology, Foraminifera, SW Iberia, Tsunami deposits

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Palaeostress inversion from post-glacial scarps on the Hellenic Subduction Forearc

Violeta Veliz Borel (1)

(1) [email protected]

Abstract: Tectonic stress magnitudes are an essential input on seismic hazard assessment to estimate the likelihood of a given rupture scenario. Absolute tectonic stress magnitudes can only be roughly estimated using several assumptions on any of the available methods. Most of those methods are based on instrumental data- sets. However, instrumental data-sets only provide small snapshots of the overall mega-thrust seismic cycle. The Hellenic subduction system has a mega-thrust seismic cycle of ~1500 - 2000 yrs, implying that the instrumental era only accounts for less than 5% of the seismic cycle. We have performed a stress inversion out of slicken-sides measured on post-glacial scarps on the islands of Kythira, Antikythira, Crete, Kassos, and Karpathos, representing the Hellenic arc in a forearc position overlying the approximate downdip end of weak seismic locking. We have determined the tectonic stress orientation since the last post-glacial era (~16.5 ka), a time window that comprehends several (~10) seismic cycles. In general, we detected that the largest principal normal stress (sigma 1) is subvertical in all localities, and the orientation of the smallest principal normal stress (sigma 3) varies along the margin producing a variety of fault orientations. Further, we found that while in the western part of the margin (Kythira, Antikythira and western Crete), the extension is subperpendicular to the trench, in the east (eastern Crete, Kasos, and Karpathos) it is subparallel to the trench. We recognized that the stress field in the upper-crust of the fore-arc calculated over many seismic cycles often differs from the stress derived from instrumental data. Because in some areas sigma 2 is similar in magnitude to sigma 3, this is most probably due to local-scale strain-partitioning and/or to fluctuations in the state of stress during the seismic cycle.

Keywords: Hellenic subduction forearc, paleostress inversion, Post-glacial

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

IPOC Creep as a natural lab: Deciphering fault slip behavior from fault gouge structure and composition and high rate instrumental monitoring with the IPOC Creepmeter array

Pia Victor (1), Ariane Müting (1), Armin Dielforder (1), Anja Schleicher (1), Gabriel Gonzalez (2), Onno Oncken (1)

(1) Helmholz Zentrum Potsdam, Deutsches GeoForschungsZentrum GFZ, Germany (2) Departamento de Ciencias Geologicas, Universidad Catolica del Norte, Antofagasta, Chile

Abstract: The partitioning between seismic and aseismic slip behavior of active faults is a valuable property to understand their hazard potential. It depends on the composition of the fault rock, temperature and pressure conditions and strain rate. For faults with extended recurrence intervals of seismic surface rupturing events, the slip accumulation pattern through time is hard to deduce beyond the instrumental time scale. It is, therefore, insufficient for estimates of their hazard potential. Fault rock textures are an essential archive of the frictional properties and behavior through time. Calibration with laboratory experiments is one method to verify structural evolution depending on composition or environmental parameters. In this study, we use decomposed creepmeter time-series of the IPOC Creepmeter array in N-Chile to directly determine the proportion of the seismic and aseismic contribution to the total slip accumulation for active segments of the Atacama Fault System (AFS) over an eight-year monitoring period. We can differentiate between slowly creeping fault segments and others, which are accumulating displacement solely by triggered shallow slip events with slip velocities up to 10-4 m/sec. As a result of this analysis, we can state that one of the fault segments preferentially creeps at shallow depth. Other segments accumulate permanent displacement by accumulation of seismic slip events. Comparing these observations with the fault zone structure and composition at the creepmeter sites is work in progress. So far, we find a remarkably clear correlation of segments exhibiting 10 cm thick fault gouge with an anastomosing network of principle slip zones and a mineralogical composition strongly dominated by gypsum and creeping fault behavior. By contrast, fault segments, accumulating displacement only via slip events, do not have a fault gouge developed. These first results demonstrate that AFS fault segments at shallow depth exhibit a spectrum of fault slip modes ranging from creep to slow earthquakes. This is closely linked to fault zone properties, therefore corroborating the ability of seismic rupture potential at shallow crustal levels.

Keywords: Active tectonics, Atacama Fault System, fault rock, displacement rates, time series analysis

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Glacial Quaternary geology of the Patagonian Andes across the Coyhaique-Puerto Aysén transect constrains neotectonics and paleoseismological observations along the Liquiñe-Ofqui Fault Zone

Angelo Villalobos (1)*, Rita Arqueros (1), Gabriel Easton (1), Gregory P. De Pascale (1)

(1) Departamento de Geología, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Plaza Ercilla 803, Santiago, Chile

Abstract: Quaternary glaciations in the Southern Andes are widely studied in the mountain areas of both the Lakes Region (e.g. Clapperton, 1993; Porter, 1981; Denton et al., 1999) and the Magellan Region (e.g. Marden et al., 1995). In the Patagonian Andes of Southern Chile this type of studies are scarce. Although, Aysén Region is an area well known for having hold the former Patagonian Ice Sheet, whose length along this mountain range is estimated up to 2,000 km long (38° - 55° S) during the Last Glacial Maximum. Ice sheets, and also mountain glaciers, leave a rich geomorphological record of their advances. Particularly, they are well represented in the eastern piedmont. This offers a great opportunity to study and understand fluctuations of the ice cover through glacial cycles. In this work, we present for the first time geomorphology, stratigraphy, and radiocarbon-based geochronology of glacial drifts in the Coyhaique River basin, Emperador Guillermo and Mañihuales rivers confluence, and close to Puerto Aysén city. Furthermore, we present evidence of buried moraines in Riesco Lake and Aysén Fjord. We focus in to determine the environmental evolution during Quaternary glaciations, and the position of the ice sheet during this period, to constrain the activity of the Liquiñe-Ofqui Fault Zone. We found that the last ice sheet retreat in this region occurred after 12 ka, constraining the maximum age of subaerial and submarine geomorphological and paleoseismological features associated to this fault zone in the area.

Keywords: Patagonian Andes, neotectonics, Quaternary geomorphology

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Exploiting local geological data for fault-based seismic risk: a Fault2SHA experience.

Francesco Visini (1), Oona Scotti (2), Joanna Faure Walker (3), Laura Peruzza (4), Bruno Pace (5), Lucilla Benedetti (6), Paolo Boncio (5), Gerald Roberts (7)

(1)….National Institute of Geophysics and Volcanology (INGV), Italy (2)….Institut de Radioprotection et de Sûreté Nucléaire, France (3)….University College London, United Kingdom (4)….National Institute of Oceanography and Experimental Geophysics (OGS), Italy (5)….University of Studies G. d'Annunzio Chieti and Pescara, Italy (6)….UMR7330 Centre Européen de Recherche et d'enseignement de Géosciences de l'environnement (CEREGE), France (7)….Birkbeck, University of London, United Kingdom

Abstract: To reduce the gap between geologists, providing data on the activity of faults, and seismic hazard/risk modelers, we propose a novel methodology that (i) enhances the use of fault data in the calculations, and (ii) improves the dialog between these two communities through a new visualization schemes showing which faults threaten specific localities the most. To illustrate our methodology, we use a fault database developed in the framework of the ESC FAULT2SHA working group (fault2sha.net) by the Central Apennines laboratory participants. This database provides geologic data in the form of characterized fault traces, grouped into faults and master faults, with individual slip rate estimates. Using this database, we were able to build detailed fault deformation models, including variable slip rate profiles and multi fault ruptures, and develop novel visualization schemes of the results. The resulting hazard and typological risk maps allow both data providers and end-users to visualize the faults that threaten specific localities the most, to appreciate the density of observations used for the computation of slip rate profiles, and the degree of confidence on the fault parameters documented in the database (activity and location certainty). Keys to this new generation of fault-based seismic hazard and risk methodology are the user-friendly open source codes documenting, step-by-step, the link between the geological database and the relative contribution of each section to seismic hazard and risk at specific localities. The methodology allows exploration of epistemic uncertainties documented in the database as well as additional parameters required to characterize the seismogenic potential of fault sources. Here we consider only one branch of the uncertainties affecting each step of the computation procedure, to illustrate the methodology and how to apply for future investigation.

Keywords: Fault2SHA experience, seismic risk

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

The Truckee River Terraces of Reno

Steven G. Wesnousky (1), Lewis A. Owen (2)

(1) Center for Neotectonic Studies and Nevada Seismological Laboratory, University of Nevada, Reno, NV 89557, USA (2) Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC 2769, USA

Abstract: The lower Truckee River exhibits in number and length the most extensive suite of strath terraces preserved along the eastern flank of the Sierra Nevada of the . Extending eastward for ~25 km from near the town of Verdi at the California border to the city of Reno in Nevada, the terraces first gained attention in the 1960’s with the studies of Peter Birkeland. He attributed the terraces to four periods of glaciation. More than 50 years later, we combine additional field observation with Lidar and 10Be terrestrial cosmogenic nuclide (TCN) dating to consider the causes contributing to abandonment and preservation of the terraces. Mapping illustrates the presence of 6 distinct terrace levels. The highest terrace rests ~110 m above the current Truckee River and observed with 10Be measurements to be ~350 ka. Deposits on the strath terraces contain granitic boulders most likely sourced from glaciated headwaters of the Truckee River some 20 km upstream from the terraces. Boulders within the deposits reach 4-12 m dimension, significantly greater than the <1 m dimension of boulders observed in the River today. The eastern limit of terraces correlates spatially with well-defined east-dipping active Sierra Nevada range-bounding normal faults. The most recent displacements are manifest by a distributed set of fault scarps and fault grabens in the youngest terrace levels. With these observations, it is interpreted that abandonment and preservation of the strath terraces is the result of an average of ~0.3 mm/a tectonic uplift localized along the rangefront and suggested that strath deposits are outwash temporally linked to glacial cycles. The observations provide new measures on which to quantify estimates of seismic hazard in the urbanized areas of Reno.

Keywords: Neotectonics, Strath Terraces, Glaciation, Cosmogenic exposure age

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10th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), November 2021, Hornitos, Chile

INQUA Focus Group on Paleoseismology and Active Tectonics

Discussion on the possibility of glacial earthquakes during mid/late MIS 2 in the southern Baltic onshore settings

Piotr Paweł Woźniak (1), Małgorzata Pisarska-Jamroży (2)

(1) Department of Geomorphology and Quaternary Geology, University of Gdańsk, Bażyńskiego 4, 80–309 Gdańsk, Poland, [email protected] (2) Institute of Geology, Adam Mickiewicz University, B. Krygowskiego 12, 61–680 Poznań, Poland, [email protected]

Abstract: Seismites (layers containing soft-sediment deformation structures produced by seismic shaking) in unconsolidated late Quaternary sediments dated at mid/late MIS 2 in intraplate settings of Latvia, Lithuania and Germany are reported in several recent works. They occur in sediments deposited either in glaciolacustrine basins in front of the advancing Fennoscandian Ice Sheet or in other settings, but still close to the ice-sheet margin. Multiple deformed layers between undeformed layers are recognized in all these sites. The deformed layers are commonly rich in load casts, pseudonodules, injection structures and fluid-escape structures. The glacial earthquakes induced by the stick-slip motion of ice, basal ice sliding or glacial calving as well as glacial isostatic adjustment linked to reactivation of bedrock faults occurred in a moat setting, and sea wave action in case of a coastal settings are considered and discussed as possible trigger mechanisms. The study has been financially supported by a grant for the GREBAL project (No. 2015/19/B/ST10/ 00661) from the National Science Centre Poland.

Keywords: Intraplate setting, Scandinavian Ice Sheet, glacial earthquakes, seismites, MIS 2

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