Subduction Zone Megathrust Earthquakes GEOSPHERE
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Shape of the Subducted Rivera and Cocos Plates in Southern Mexico
JOURNALOF GEOPHYSICAL RESEARCH, VOL. 100, NO. B7, PAGES 12,357-12,373, JULY 10, 1995 Shapeof the subductedRivera and Cocosplates in southern Mexico: Seismic and tectonicimplications Mario Pardo and Germdo Sufirez Insfitutode Geoffsica,Universidad Nacional Aut6noma de M6xico Abstract.The geometry of thesubducted Rivera and Cocos plates beneath the North American platein southernMexico was determined based on the accurately located hypocenters oflocal and te!eseismicearthquakes. The hypocenters ofthe teleseisms were relocated, and the focal depths of 21 eventswere constrainedusing a bodywave inversion scheme. The suductionin southern Mexicomay be approximated asa subhorizontalslabbounded atthe edges by the steep subduction geometryof theCocos plate beneath the Caribbean plate to the east and of theRivera plate beneath NorthAmerica to thewest. The dip of theinterplate contact geometry is constantto a depthof 30 kin,and lateral changes in thedip of thesubducted plate are only observed once it isdecoupled fromthe overriding plate. On thebasis of theseismicity, the focal mechanisms, and the geometry ofthe downgoing slab, southern Mexico may be segmented into four regions ß(1) theJalisco regionto thewest, where the Rivera plate subducts at a steepangle that resembles the geometry of theCocos plate beneath the Caribbean plate in CentralAmerica; (2) theMichoacan region, where thedip angleof theCocos plate decreases gradually toward the southeast, (3) theGuerrero-Oaxac.a region,bounded approximately by theonshore projection of theOrozco and O'Gorman -
Geotechnical Reconnaissance of the 2015 Mw8.3 Illapel, Chile Earthquake
GEOTECHNICAL EXTREME EVENTS RECONNAISSANCE (GEER) ASSOCIATION Turning Disaster into Knowledge Geotechnical Reconnaissance of the 2015 Mw8.3 Illapel, Chile Earthquake Editors: Gregory P. De Pascale, Gonzalo Montalva, Gabriel Candia, and Christian Ledezma Lead Authors: Gabriel Candia, Universidad del Desarrollo-CIGIDEN; Gregory P. De Pascale, Universidad de Chile; Christian Ledezma, Pontificia Universidad Católica de Chile; Felipe Leyton, Centro Sismológico Nacional; Gonzalo Montalva, Universidad de Concepción; Esteban Sáez, Pontificia Universidad Católica de Chile; Gabriel Vargas Easton, Universidad de Chile. Contributing Authors: Juan Carlos Báez, Centro Sismológico Nacional; Christian Barrueto, Pontificia Universidad Católica de Chile; Cristián Benítez, Pontificia Universidad Católica de Chile; Jonathan Bray, UC Berkeley; Alondra Chamorro, Pontificia Universidad Católica de Chile; Tania Cisterna, Universidad de Concepción; Fernando Estéfan Thibodeaux Garcia, UC Berkeley; José González, Universidad de Chile; Diego Inzunza, Universidad de Concepción; Rosita Jünemann, Pontificia Universidad Católica de Chile; Benjamín Ledesma, Universidad de Concepción; Álvaro Muñoz, Pontificia Universidad Católica de Chile; Antonio Andrés Muñoz, Universidad de Chile; José Quiroz, Universidad de Concepción; Francesca Sandoval, Universidad de Chile; Pedro Troncoso, Universidad de Concepción; Carlos Videla, Pontificia Universidad Católica de Chile; Angelo Villalobos, Universidad de Chile. GEER Association Report No. GEER-043 Version 1: December 10, 2015 FUNDING -
Estimation of a Source Model and Strong Motion Simulation for Tacna City, South Peru
Estimation of a Source Model and Strong Motion Simulation for Tacna City, South Peru Paper: Estimation of a Source Model and Strong Motion Simulation forTacnaCity,SouthPeru Nelson Pulido∗1, Shoichi Nakai∗2, Hiroaki Yamanaka∗3, Diana Calderon∗4, Zenon Aguilar∗4, and Toru Sekiguchi∗2 ∗1National Research Institute for Earth Science and Disaster Prevention 3-1 Tennodai, Tsukuba, Ibaraki 305-0006, Japan E-mail: [email protected] ∗2Chiba University, Chiba, Japan ∗3Tokyo Institute of Technology, Kanagawa, Japan ∗4Universidad Nacional de Ingenier´ıa, Per´u, Lima, Per´u [Received August 18, 2014; accepted September 8, 2014] We estimate several scenarios for source models of megathrust earthquakes likely to occur on the Nazca- South American plates interface in southern Peru. To do so, we use a methodology for estimating the slip distribution of megathrust earthquakes based on an interseismic coupling (ISC) distribution model in subduction margins and on information about his- torical earthquakes. The slip model obtained from geodetic data represents large-scale features of asper- ities within the megathrust that are appropriate for simulating long-period waves and tsunami modelling. To simulate broadband frequency strong ground mo- tions, we add small scale heterogeneities to the geode- tic slip by using spatially correlated random noise dis- tributions. Using these slip models and assuming sev- eral hypocenter locations, we calculate a set of strong ground motions for southern Peru and incorporate site effects obtained from microtremors array surveys in Tacna, the southernmost city in Peru. Keywords: strong motion, source process, 1868 earth- quake, seismic hazard, South Peru Fig. 1. Slip deficit in southern Peru and northern Chile 1. -
Damage Assessment of the 2015 Mw 8.3 Illapel Earthquake in the North‑Central Chile
Natural Hazards https://doi.org/10.1007/s11069-018-3541-3 ORIGINAL PAPER Damage assessment of the 2015 Mw 8.3 Illapel earthquake in the North‑Central Chile José Fernández1 · César Pastén1 · Sergio Ruiz2 · Felipe Leyton3 Received: 27 May 2018 / Accepted: 19 November 2018 © Springer Nature B.V. 2018 Abstract Destructive megathrust earthquakes, such as the 2015 Mw 8.3 Illapel event, frequently afect Chile. In this study, we assess the damage of the 2015 Illapel Earthquake in the Coquimbo Region (North-Central Chile) using the MSK-64 macroseismic intensity scale, adapted to Chilean civil structures. We complement these observations with the analysis of strong motion records and geophysical data of 29 seismic stations, including average shear wave velocities in the upper 30 m, Vs30, and horizontal-to-vertical spectral ratios. The calculated MSK intensities indicate that the damage was lower than expected for such megathrust earthquake, which can be attributable to the high Vs30 and the low predominant vibration periods of the sites. Nevertheless, few sites have shown systematic high intensi- ties during comparable earthquakes most likely due to local site efects. The intensities of the 2015 Illapel earthquake are lower than the reported for the 1997 Mw 7.1 Punitaqui intraplate intermediate-depth earthquake, despite the larger magnitude of the recent event. Keywords Subduction earthquake · H/V spectral ratio · Earthquake intensity 1 Introduction On September 16, 2015, at 22:54:31 (UTC), the Mw 8.3 Illapel earthquake occurred in the Coquimbo Region, North-Central Chile. The epicenter was located at 71.74°W, 31.64°S and 23.3 km depth and the rupture reached an extent of 200 km × 100 km, with a near trench rupture that caused a local tsunami in the Chilean coast (Heidarzadeh et al. -
The 2014 Earthquake in Iquique, Chile: Comparison Between Local Soil Conditions and Observed Damage in the Cities of Iquique and Alto Hospicio
The 2014 Earthquake in Iquique, Chile: Comparison between Local Soil Conditions and Observed Damage in the Cities of Iquique and Alto Hospicio Alix Becerra,a) Esteban Sáez,a),b) Luis Podestá,a),b) and Felipe Leytonc) In this study, we present comparisons between the local soil conditions and the observed damage for the 1 April 2014 Iquique earthquake. Four cases in which site effects may have played a predominant role are analyzed: (1) the ZOFRI area, with damage in numerous structures; (2) the port of Iquique, in which one pier suffered large displacements; (3) the Dunas I building complex, where soil-structure interaction may have caused important structural damage; and (4) the city of Alto Hospicio, disturbed by the effects of saline soils. Geophysical characterization of the soils was in agreement with the observed damage in the first three cases, while in Alto Hospicio the earthquake damage cannot be directly related to geophysical characterization. [DOI: 10.1193/ 111014EQS188M] INTRODUCTION On 1 April 2014, a MW 8.2 earthquake occurred in northern Chile, northwest of the town of Iquique; the main shock was followed by a MW 7.7 aftershock two days later (Figure 1). The 2014 Iquique earthquake was caused by the thrust faulting between the Nazca and South America plates. The rupture area had a length of about 200 km and a hypocenter depth of 38.9 km, according to the Chilean Seismological Center earthquake report. Prior to this event, northern Chile was characterized by a seismic quiescence of 136 years (known as the “Iquique seismic gap”; Comte and Pardo 1991). -
Forming a Mogi Doughnut in the Years Prior to and Immediately
RESEARCH LETTER Forming a Mogi Doughnut in the Years Prior to and 10.1029/2020GL088351 Immediately Before the 2014 M8.1 Iquique, Key Points: • Seismicity in the years prior to and Northern Chile, Earthquake immediately before the mainshock B. Schurr1 , M. Moreno2 , A. M. Tréhu3 , J. Bedford1 , J. Kummerow4,S.Li5 , form two halves of a “Mogi 1 Doughnut” surrounding the main and O. Oncken slip patch 1 2 • Mechanical asperity model predicts Deutsches GeoForschungsZentrum‐GFZ, Section Lithosphere Dynamics, Potsdam, Germany, Departamento de stress increase where earthquakes Geofísica, Universidad de Concepción, Concepción, Chile, 3College of Earth, Ocean, and Atmospheric Sciences, Oregon are observed State University, Corvallis, OR, USA, 4Department of Earth Sciences, Freie Universität Berlin, Berlin, Germany, • Slip region correlates with high 5Earthquake Research Institute, The University of Tokyo, Tokyo, Japan interseismic locking and a circular gravity low, suggesting that the asperity is controlled by geologic structure Abstract Asperities are patches where the fault surfaces stick until they break in earthquakes. Locating asperities and understanding their causes in subduction zones is challenging because they are generally Supporting Information: located offshore. We use seismicity, interseismic and coseismic slip, and the residual gravity field to map the • Supporting Information S1 asperity responsible for the 2014 M8.1 Iquique, Chile, earthquake. For several years prior to the mainshock, seismicity occurred exclusively downdip of the asperity. Two weeks before the mainshock, a series of foreshocks first broke the upper plate then the updip rim of the asperity. This seismicity formed a ring Correspondence to: B. Schurr, around the slip patch (asperity) that later ruptured in the mainshock. -
The Chiloé Mw 7.6 Earthquake of 25 December 2016 in Southern Chile and Its Relation to the Mw 9.5 1960 Valdivia Earthquake
2016 Chiloé Earthquake, Southern Chile submitted to Geophysical Journal International The Chiloé Mw 7.6 earthquake of 25 December 2016 in Southern Chile and its relation to the Mw 9.5 1960 Valdivia earthquake 1 2 3 3 Dietrich Lange , Javier Ruiz , Sebastián Carrasco , Paula Manríquez (1) GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany (2) Departamento de Geofísica, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile (3) National Seismological Centre, University of Chile, Santiago, Chile Keywords: 2016 Chiloé earthquake, Subduction Zone, Southern Chile, 1960 Valdivia Earthquake Corresponding author: Dietrich Lange (email: [email protected]) Abstract On 25 December 2016, a Mw 7.6 earthquake broke a portion of the Southern Chilean subduction zone south of Chiloé Island, located in the central part of the Mw 9.5 1960 Valdivia earthquake. This region is characterized by repeated earthquakes in 1960 and historical times with very sparse interseismic activity due to the subduction of a young (~15 Ma), and therefore hot, oceanic plate. We estimate the co-seismic slip distribution based on a kinematic finite fault source model, and through joint inversion of teleseismic body waves and strong motion data. The coseismic slip model yields a total seismic moment of 3.94×1020 Nm that occurred over ~30 s, with the rupture propagating mainly downdip, reaching a peak-slip of ~4.2 m. Regional moment tensor inversion of stronger aftershocks reveals thrust type faulting at depths of the plate interface. The fore- and aftershock seismicity is mostly related to the subduction interface with sparse seismicity in the overriding crust. -
Seismic Performance of Tailings Sand Dams in Chile
16th World Conference on Earthquake, 16WCEE 2017 Santiago Chile, January 9th to 13th 2017 Paper N° 4230 Registration Code: S-V1461865061 Seismic performance of tailings sand dams in Chile J. H. Troncoso (1), R. Verdugo (2), L. Valenzuela (3) (1) Senior Geotechnical Consultant, MWH Chile, (2) Senior geotechnical Consultant, CMGI Consultants (3) Geotechnical Consultant, formerly at Arcadis Abstract An extremely high and frequent seismic activity coincides in Chile with the existence of numerous tailings dams associated to the copper industry. In the country there is a history of tailings dam failures since the early XX century and up to today. Nevertheless since the decade of 1960 there have been a growing number of new large tailings dams that have had a very good performance even when subjected to very strong earthquakes. The paper summarizes the instructive history of failures as well as of successes of the newly designed tailings dams and particularly of the sand tailings dams. Different aspects of the main new sand tailings dams such as the design criteria, tailings sand characteristics under high confining stresses are discussed. These aspects are complemented with information on major earthquakes occurred in Chile in the last years, especially of El Maule Earthquake of Magnitude 8.8 of February 27, 2010 and the location of main tailings dams in the zones impacted by this earthquake. Finally, discussions are included with regard general seismic performance of tailings sand dams, seismic deformations, and seismic instrumentation including dams in operation and dams already inactive. Keywords: Tailings dams, Seismic behavior, Sand dams, Tailings sands, Dynamic properties of sands. -
The Delayed Aftershocks of the Illapel Earthquake Mw 8.3, 2015, Chile
EGU21-6978 https://doi.org/10.5194/egusphere-egu21-6978 EGU General Assembly 2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. The delayed aftershocks of the Illapel Earthquake Mw 8.3, 2015, Chile Franco Lema1 and Mahesh Shrivastava1,2 1Departamento de Ciencias Geológicas, Universidad Católica del Norte, Antofagasta, Chile ([email protected]) 2National Research Center for Integrated Natural Disaster Management, Santiago, Chile ([email protected]) The delayed aftershocks 2018 Mw 6.2 on April 10 and Mw 5.8 on Sept 1 and 2019 Mw 6.7 on January 20, Mw 6.4 on June 14, and Mw 6.2 on November 4, associated with the Mw 8.3 2015 Illapel Earthquake occurred in the central Chile. The seismic source of this earthquake has been studied with the GPS, InSAR and tide gauge network. Although there are several studies performed to characterize the robust aftershocks and the variations in the field of deformation induced by the megathrust, but there are still aspects to be elucidated of the relationship between the transfer of stresses from the interface between plates towards delayed aftershocks with the crustal structures with seismogenic potential. Therefore, the principal objective of this study is to understand how the stress transfer induced by the 2015 Illapel earthquake of the heterogeneous rupture mechanism to intermediate-deep or crustal earthquakes. For this, coulomb stress changes from finite fault model of the Illapel earthquake and with the biggest aftershocks in year 2015 are used. These cumulative stress pattern provides substantial evidences for the delayed aftershocks in this region. -
A Lacuna Sísmica Do Norte Do Chile: Estado Da Arte
! ! ! ! "#$%&'!&'#!()*+')*#!&*!(*)),!&*! ! -'.$*#!/0,)'#1!-21!&*!34536! ! ! ! ! ! ! ! ! ! ! ! ! 7.89*)#8&,&*!&*!:;'!<,%0'!=7:<>!!*!!7.89*)#8&,&*!&*!?),#@08,!=7.?>! ! ! ! ! Centro de Sismologia da USP IAG / IEE !!!!/*.$)'!&*!:8#+'0'A8,!&,!7:<!=BC2DB"">! ! ! :B:D7.?E!FG#*)9,$H)8'!:8#+'0HA8I'!&,!7.?! ! ! A lacunaJ*0,$H)8'!!&*!! sísmica55K4LK345L do! Norte do Chile: estado da arte ! "! Hans Agurto-Detzel São Paulo, 15-Setembro-2014 B05310 SCHOLZ AND CAMPOS: SEISMIC COUPLING B05310 Figure 4. The earthquake history and coupling of Chile. See text for sources of couplingScholz and Campos, 2012. data. JGR Ward [1990] as far as 400 km downdip. Because we study concluded it was fully coupled on a 20 dipping surface only the seismogenic portion of the interface, for our cal- down to 35 km depth, below which the coupling linearly culations we use the geodetic estimates of the moment. tapered to zero at 55 km. By the same reasoning as discussed Lorenzo-Martin et al. [2006] found, from GPS measure- in the Cascadia case, we take the fully locked region to be ments, that c = 0.96 for A = 110 109m2 and an assumed the seismogenic area. This boundary seems to have been G c  subduction velocity of 69 mm/yr, yielding P_ G = 7.3 F. defined by the Mw 7.7 Tocopilla earthquake of 2007, in [65] The only known preceding earthquake of size similar which its region of maximum slip was concentrated around to the 1960 event was one that occurred in 1575 [Cisternas 35 km, with some slip, possibly post-seismic, extending to 50 km depth [Bejar-Pizarro et al., 2010]. -
Seismic Loss Estimation Model for Mexico City
1902 SEISMIC LOSS ESTIMATION MODEL FOR MEXICO CITY Mario ORDAZ1, Eduardo MIRANDA2, Eduardo REINOSO3 And Luis Eduardo PÉREZ-ROCHA4 SUMMARY A loss estimation model for Mexico City is presented. The approach is designed for insurance purposes, in order to compute pure premiums and probable maximum losses in portfolios of buildings. Some of its main features are the following: Earthquake motions are characterised in terms of acceleration response spectra, so both intensity and frequency content are accounted for. The model uses response spectra at a firm site as a reference point to compute response spectra at soft sites. The reference spectra are computed using semi-empirical spectral attenuation laws, some of which were derived from accelerographic information recorded in Mexico during the past 35 years. Response spectrum transfer functions are used to compute response spectra at lakebed-zone accelerometric stations. For sites other than accelerometric stations, an original interpolation procedure is employed. From the acceleration spectra and general structural characteristics, the maximum inter-storey drift ratio is estimated using a simplified model, which consists on a combination of flexural and shear vertical cantilever beams. The approach uses displacement-based vulnerability functions to estimate the damage ratio from the maximum inter-storey drift. Based on this inter-story drift, a probability density function is obtained to compute the expected annual loss and the probable maximum loss of the structure. INTRODUCTION In recent years, especially after the devastating earthquake of September 19, 1985, there has been a great advance in many aspects of earthquake engineering in Mexico. In particular, soil effects in Mexico City have been thoroughly investigated, new methods for the evaluation of structural response and damage have been developed, and several attenuation studies have been carried out with the use of the several sate-of-the-art strong-motion networks installed in the country. -
Continuing Megathrust Earthquake Potential in Chile After the 2014 Iquique Earthquake
LETTER doi:10.1038/nature13677 Continuing megathrust earthquake potential in Chile after the 2014 Iquique earthquake Gavin P. Hayes1, Matthew W. Herman2, William D. Barnhart1, Kevin P. Furlong2,Seba´stian Riquelme3, Harley M. Benz1, Eric Bergman4, Sergio Barrientos3, Paul S. Earle1 & Sergey Samsonov5 The seismic gap theory1 identifies regions of elevated hazard based a seismic hazard perspective is that the fault can host another event of on a lack of recent seismicity in comparison with other portions of a a similar magnitude. Although a great-sized earthquake here had been fault.It has successfully explained past earthquakes(see, for example, expected, it is possible that this event was not it10. ref. 2) and is useful for qualitatively describing where large earth- Sections of this subduction zone have ruptured since 1877 (Fig. 1), quakes might occur. A large earthquake had been expected in the most notably in 1967, in a M 7.4 event between ,21.5u Sand22u S, and subduction zone adjacent to northern Chile3–6, which had not rup- inthe 2007 M 7.7 Tocopillaearthquake between ,22u Sand23.5u S.Slip tured in a megathrust earthquake since a M 8.8 event in 1877. On during these events was limited to the deeper extent of the seismogenic 1 April 2014 a M 8.2 earthquake occurred within this seismic gap. zone, leaving shallower regions unruptured6,11. Farther south, the 1995 Here we present an assessment of the seismotectonics of the March– M 8.1 Antofagasta earthquake broke the seismogenic zone immediately April 2014 Iquique sequence, including analyses of earthquake reloca- south of the Mejillones Peninsula, a feature argued to be a persistent bar- tions, moment tensors, finite fault models, moment deficit calculations rier to rupture propagation11,12.