DOCSLIB.ORG

Lecture 15, Slides (Pdf)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Lecture 15, Slides (Pdf) Magnitude Seismic moment Intensity Frequency-magnitude relation Earthquake magnitude Earthquake magnitude is a measure of the size or strength of an earthquake. It is based on amplitudes of seismograms. In the past various magnitude scales have been developed. Local magnitude “Richter scale” (local magnitude, ML ) was introduced by Charles Richter in 1935 for southern California earthquakes measured on a Wood-Anderson seismograph. �� = log � + 2.76 log ∆ − 2.48 ML : local magnitude A: amplitude on Wood-Anderson seismograph in mm Δ: epicentral distance in km Various magnitude scales Body wave magnitude Correction term body wave magnitude Surface wave magnitude Earthquakes vs. nuclear explosions Body and surface wave magnitude have been used to discriminate between nuclear explosions and earthquakes. Body and surface wave magnitude ‘Saturation’ is a problem of body and surface wave magnitudes Seismic moment, moment magnitude ML , mb , MS are empirical. Better: Seismic moment M0 = μ D S μ : shear modulus [Pa = Nm-2] D : average slip along fault plane [m] S : surface area along which slip occurred [m2] M0 in Nm, i.e. a measure of energy or moment/torque Related magnitude scale: Moment magnitude log � � = 0 − 10.73 � 1.5 -5 -2 -7 where M0 in ergs = dyne . cm = 10 N . 10 m = 10 Nm !"# $ (or � = ! − 6 with M in Nm) � %.' 0 Seismic energy Empirical relation between seismic energy (ES) and MW : 10 log ES = 1.5 MW + 11.8 1 unit increase in MW corresponds to a 32 time increase in ES Note that seismic energy is only a fraction of the total energy released during an earthquake. Fracture energy and heat are (more) important. Frequency, magnitude and energy release 26-12-2004, Mw 9.1, Sumatra earthquake Lay et al, 2005 Ammon et al, 2005 26-12-2004, Mw 9.1, Sumatra earthquake - tsunami Lay et al, 2005 Magnitude vs. Intensity Earthquake magnitude is measure of size of an earthquake and can be negative. Seismic intensity is a measure of the effects of ground shaking caused by an earthquake. There are various, slightly different, intensity scales Intensity is expressed in roman numerals: I – XII, or I – X. Modified Mercalli intensity scale Intensities for the 1989, Mw 6.9, Loma Prieta earthquake USGS 1989, Mw 6.9, Loma Prieta earthquake in San Francisco Mariana district (artificial fill) Seismicity in the Netherlands KNMI 1992 Roermond earthquake Intensities of Roermond earthquake of 13 April 1992 ML = 5.8, Mw = 5.3 Depth: 18 km Frequency-magnitude relation Frequency-magnitude (or Gutenberg-Richter) relation log � = � − �� N : number of earthquakes with magnitude greater than M within certain time span (e.g. year) for region. b : slope, relative occurrence of large compared to small earthquakes b ~ 1 (typically 0.7 – 1.3) a: 10a is number of earthquakes (in that region for time span) Relation was found empirically and suggests self-similarity or fractal scaling (scale invariance). Frequency-magnitude relation Deviations from log � = � − �� at high and low M. Deviations at small M can be due to ... Deviation at large M can be due to ... Frequency-magnitude relation log � = � − �� N : all earthquakes with magnitude larger than 0 Alternatively, log � = �′ − �(� − ����) N : all earthquakes with magnitude larger than ���� Frequency-magnitude relation Seismicity for Rhenish Massif and Lower Rhine Graben Ahorner, 1983 Earthquakes with magnitude similar to the Roermond earthquake of 1992 happen once every ~ 200 years. The previous one was in 1756. Earthquake prediction vs earthquake hazard In earthquake prediction, earthquakes are predicted with specified time location and magnitude. True earthquake prediction of major earthquakes is not possible in the foreseeable future. Yet, there may be signs of an impending earthquake (foreshocks, Radon emission, changes in ground water level, strange animal behavior). Seismic hazard analysis uses the statistics of (past) earthquakes. Seismic hazard Europe Grünthal et al. peak ground acceleration with 10% probability in 50 years Induced seismicity Grigoli et al. 2017 Induced seismicity: Largest earthquakes per site Grigoli et al. 2017 Seismic hazard USA USGS Ground acceleration with a 2% chance of being exceeded over a period of 50 years. Note hazard caused by induced earthquakes in Oklahoma (hexagon)..
Load more

Recommended publications
  • 4Th Annual Report
    UK EARTHQUAKE MONITORING 1992/93 BGS Seismic Monitoring and Information Service Fourth Annual Report British Geological Survey Tel: 0131-667-1000 Murchison House Fax: 0131-667-1877 West Mains Road Internet: http://www.gsrg.nmh.ac.uk/ Edinburgh EH9 3LA Scotland BRITISH GEOLOGICAL SURVEY TECHNICAL REPORT WL/93/08 Global Seismology Series UK Earthquake Monitoring 1992/93 BGS Seismic Monitoring and Information Service Fourth Annual Report C W A Browitt and A B Walker April 1993 UK Seismic Monitoring and Information Service Year Four Report to Customer Group: April 1993 Cover photo Solar-powered earthquake- monitoring station in the North-west Highlands of Scotland (T Bain) Bibliographic reference Browitt, C W A & Walker, A B., 1993. BGS Seismic Monitoring and Information Service Fourth Annual Report. British Geological Survey Technical Report WL/93/08 @ NERC Copyright 1993 Edinburgh British Geological Survey 1993 BRITISH GEOLOGICAL SURVEY The full range of Survey publications is available Keyworth, Nottingham NG 12 5GG through the Sales Desks at Keyworth and at B 0602-363 100 Telex 378173 BGSKEY G Murchison House, Edinburgh, and in the BGS Fax0602-363200 London Information Office in the Natural History Museum Earth Galleries. The adjacent bookshop Murchison House, West Mains Road, Edinburgh stocks the more popular books for sale over the EH93LA counter. Most BGS books and reports are listed in Telex 727343 SEISED G HMSO’s Sectional List 45, and can be bought from s 031-667 1000 Fax031-6682683 HMSO and through HMSO agents and retailers. Maps are listed in the BGS Map Catalogue, and can be bought from BGS approved stockists and agents London Information Office at the Natural History as well as direct from BGS.
    [Show full text]
  • Review of Geotechnical Investigations Resulting from the Roermond April 13, 1992 Earthquake
    Missouri University of Science and Technology Scholars' Mine International Conferences on Recent Advances 1995 - Third International Conference on Recent in Geotechnical Earthquake Engineering and Advances in Geotechnical Earthquake Soil Dynamics Engineering & Soil Dynamics 07 Apr 1995, 10:30 am - 11:30 am Review of Geotechnical Investigations Resulting from the Roermond April 13, 1992 Earthquake P. M. Maurenbrecher TU Delft, The Netherlands A. Den Outer TU Delft, The Netherlands H. J. Luger Delft Geotechnics, The Netherlands Follow this and additional works at: https://scholarsmine.mst.edu/icrageesd Part of the Geotechnical Engineering Commons Recommended Citation Maurenbrecher, P. M.; Den Outer, A.; and Luger, H. J., "Review of Geotechnical Investigations Resulting from the Roermond April 13, 1992 Earthquake" (1995). International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics. 5. https://scholarsmine.mst.edu/icrageesd/03icrageesd/session09/5 This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License. This Article - Conference proceedings is brought to you for free and open access by Scholars' Mine. It has been accepted for inclusion in International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics by an authorized administrator of Scholars' Mine. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. (\ Proceedings: Third International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, t..\ April 2-7, 1995, Volume II, St. Louis, Missouri Review of Geotechnical Investigations Resulting from the Roermond April 13, 1992 Earthquake Paper No.
    [Show full text]
  • Smallest Earthquake Magnitude That Can Trigger Liquefaction
    Smallest Earthquake Magnitude that Can Trigger Liquefaction Russell Green, Julian Bommer Datum June 2018 Editors Jan van Elk & Dirk Doornhof General Introduction The soils in Groningen contain deposits of water saturated sands. Therefore, the possibility of earthquake- induced liquefaction needs to be considered. In particular, liquefaction could potentially be important for critical infra-structure like dikes and levees. This report contains a literature study of field observations, to establish an earthquake magnitude threshold below which the possibility of triggering liquefaction can be discounted. The study concludes that earthquakes as small as moment magnitude 4.5 can trigger liquefaction in extremely susceptible soil deposits. However, these susceptible soil deposits correspond to site conditions where building construction is not viable. Example of such extremely susceptible soil deposits would be a mud-flat area outside the dikes, a river bed, an impoundment area or a tailings pond. For soil profiles that are sufficiently competent to support foundation loads, the minimum earthquake magnitude for the triggering of liquefaction is about 5. The report therefore proposes that in liquefaction hazard assessments for engineering applications, magnitude 5.0 be adopted as the minimum earthquake size considered. Title Smallest Earthquake Magnitude that Can Trigger Date June 2018 Liquefaction Initiator NAM Autor(s) Russell Green and Julian Bommer Editor Jan van Elk Dirk Doornhof Organisation Team of Academic Experts Organisation NAM Place in the Study Study Theme: Liquefaction and Data Comment: Acquisition Plan The soils in Groningen contain deposits of water saturated sands. Therefore, the possibility of earthquake-induced liquefaction needs to be considered. In particular, liquefaction could potentially be important for critical infra-structure like dikes and levees.
    [Show full text]
  • Local Administrations and Disaster Risk Management In
    DISASTER RESILIENT URBAN SETTLEMENTS A DOCTORAL DISSERTATION SUBMITTED TO THE FACULTY OF SPATIAL PLANNING OF TECHNICAL UNIVERSITY OF DORTMUND BY EBRU ALARSLAN IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF ENGINEERING (Dr. Ing.) IN SPATIAL PLANNING DECEMBER 2009 I hereby declare that all information in this document has been obtained and presented in accordance with academic rules and ethical conduct. I also declare that, as required by these rules and conduct, I have fully cited and referenced all material and results that are not original to this work. Name, Last name: Ebru ALARSLAN Signature : ii ABSTRACT DISASTER RESILIENT URBAN SETTLEMENTS Alarslan, Ebru Dr. Ing. In Spatial Planning, Faculty of Spatial Planning Supervisors:Prof.Dr. Stefan Greiving, Prof.Dr.H.Hans Blotevogel, Prof.Dr. Konstantin Meskouris September 2009, 480 pages Recently, natural disasters with devastating effects on human settlements have proliferated. Against this background, this study outlines a resilience model for urban settlements with respect to natural disasters. The focus on urban settlements has been chosen because of their high disaster risks due to (i) their dense population and construction, (ii) their position as a center of economic and cultural activities, (iii) their location on the significant cross-roads of transportation routes and other modern networks, and (iv) their exploitation of natural resources and generation of environmental pollution. In addition to these reasons, variables of disaster risks in urban settlements
    [Show full text]
  • Assessing Damage for Herkenbosch, the Netherlands, Due to The
    Transactions on the Built Environment vol 14, © 1995 WIT Press, www.witpress.com, ISSN 1743-3509 Assessing damage for Herkenbosch, The Netherlands, due to the Roermond earthquake of April 13, 1992 P.M. Maurenbrecher, G. de Vries Faculty of Mining and Petroleum Engineering, University of 2629 Abstract During the April 13 1992 Roermond earthquake the town of Herkenbosch suffered extensive damage. To examine the extent of the damage a door to door enquiry survey was carried out. 75% of the households replied to the survey, which is based on "yes" or "no" replies to questions on the residents' experience during the earthquake, the damage to their homes and other observations. The replies were entered into a database. Examples of selected replies are given to show their geographical distribution. The study requires further input data to enable more effective use of the information. To facilitate this, the present database is structured in a way that further information can be easily added; for example reports from the Rampenfonds (Disaster Fund) survey, municipality information on house lay-outs and building details, and ground conditions. With sufficient data the survey should indicate which house styles or building methods are vulnerable to earthquake damage and identify those factors which influence such damage. 1. Introduction Subsequent to earthquakes two types of damage survey are normally carried out; one for reparations and one for research. In the Netherlands several surveys were executed soon after the Roermond earthquake; one for the Disaster Fund and a macroseismic KNMI survey *\ In addition an earthquake survey team from the UK visited Heinsberg in Germany and Roermond in the Netherlands^.
    [Show full text]
  • Earthquakes Near the Haiyuan Fault Gansu, China)
    Geophys. J. Int. 12001) 144, 206±220 Source parameters and tectonic origin of the 1996 June 1 Tianzhu Mw=5.2) and 1995 July 21 Yongden Mw=5.6) earthquakes near the Haiyuan fault Gansu, China) C. Lasserre,1 B. Bukchin,2 P. Bernard,3 P. Tapponnier,1 Y. Gaudemer,1 A. Mostinsky2 and RongDailu 4 1 Laboratoire de Tectonique et MeÂcanique de la LithospheÁre, CNRS UMR 7578, Institut de Physique du Globe de Paris, Paris, France. E-mail:[email protected] 2 International Institute of Earthquake Prediction and Mathematical Geophysics, Moscow, Russia. E-mail: [email protected] 3 Laboratoire de Sismologie, CNRS UMR 7580, Institut de Physique du Globe de Paris, Paris, France 4 Seismological Institute of Lanzhou, China Seismological Bureau, Lanzhou, Gansu, China Accepted 2000 August 25. Received 2000 August 21; in original form 2000 February 22 SUMMARY The 1996 June 1 Tianzhu 1Mw=5.2, Ms=4.9) and the 1995 July 21 Yongden 1Mw=5.6, Ms=5.4) earthquakes are the two largest events recorded in the last 10 years between the 1990 October 20 Ms=5.8 and the recent 2000 June 6 Ms=5.6 earthquakes near the `Tianzhu seismic gap' on the Haiyuan fault in northeastern Tibet. We use frequency± time analysis 1FTAN) to extract the fundamental modes of Love and Rayleigh waves from digital records. A joint inversion of their amplitude spectra and of P-wave ®rst- motion polarities is then performed to calculate the source parameters 1focal mech- anisms, depths and seismic moments) of these two Msc5 earthquakes. Such a joint inversion is tested for the ®rst time.
    [Show full text]
  • Camelbeeck Seismicity Fidgeo-3866
    Historical Earthquakes, Paleoseismology, Neotectonics and Seismic Hazard: New Insights and Suggested Procedures DOI: 10.23689/fidgeo-3866 How well does known seismicity between the Lower Rhine Graben and southern North Sea reflect future earthquake activity? Thierry Camelbeeck1, Kris Vanneste1, Koen Verbeek1, David Garcia-Moreno1,2, Koen van Noten1 & Thomas Lecocq1 1 Royal Observatory of Belgium: [email protected], [email protected], [email protected], [email protected], [email protected] 2 University of Ghent: [email protected] Abstract th Since the 14 century, moderate seismic activity with 14 earthquakes of magnitude MW≥5.0 occurred in Western Europe in a region extending from the Lower Rhine Graben (LRG) to the southern North Sea. In this paper, we investigate how well this seismic activity could reflect that of the future. The observed earthquake activity in the LRG is continuous and concentrates on the Quaternary normal faults delimiting the LRG, which are also the source of large surface rupturing Holocene and Late Pleistocene earthquakes. The estimated magnitude of these past earthquakes ranges from 6.3±0.3 to 7.0±0.3 while their average recurrence on individual faults varies from ten thousand to a few ten thousand years, which makes foreseeing future activity over the long-term possible. Three of the largest historical earthquakes with MW≥5.5 occurred outside the LRG. Late Quaternary activity along the fault zones suspected to be the source of two of these earthquakes, i.e. the 1580 Strait of Dover and 1692 northern Belgian Ardennes earthquakes, is very elusive if it exists.
    [Show full text]
  • Basin-Related Effects on Ground Motion for Earthquake Scenarios In
    Geophys. J. Int. (2006) 166, 197–212 doi: 10.1111/j.1365-246X.2006.02909.x Basin-related effects on ground motion for earthquake scenarios in the Lower Rhine Embayment ∗ Michael Ewald,1 Heiner Igel,1 Klaus-G¨unterHinzen2 and Frank Scherbaum3 1Department of Earth and Environmental Studies, Section Geophysics, Ludwig-Maximilians-University M¨unchen, Germany 2Abt. f¨urErdbebengeologie, University Cologne, Germany 3Institut f¨urGeowissenschaften, University of Potsdam, Germany Accepted 2006 January 11. Received 2006 January 8; in original form 2005 March 20 Downloaded from https://academic.oup.com/gji/article/166/1/197/632062 by guest on 24 September 2021 SUMMARY The deterministic calculation of earthquake scenarios using complete waveform modelling plays an increasingly important role in estimating shaking hazard in seismically active regions. Here we apply 3-D numerical modelling of seismic wave propagation to M 6+ earthquake scenarios in the area of the Lower Rhine Embayment, one of the seismically most active regions in central Europe. Using a 3-D basin model derived from geology, borehole information and seismic experiments, we aim at demonstrating the strong dependence of ground shaking on hypocentre location and basin structure. The simulations are carried out up to frequencies of ca. 1 Hz. As expected, the basin structure leads to strong lateral variations in peak ground motion, amplification and shaking duration. Depending on source–basin–receiver geometry, the effects correlate with basin depth and the slope of the basin flanks; yet, the basin also affects peak ground motion and estimated shaking hazard thereof outside the basin. Comparison with measured seismograms for one of the earthquakes shows that some of the main characteristics of the wave motion are reproduced.
    [Show full text]
  • Path and Site Effects Deduced from Transfrontier Internet Macroseismic Data of Two Recent M4 Earthquakes in NW Europe
    Solid Earth Discuss., doi:10.5194/se-2016-150, 2016 Manuscript under review for journal Solid Earth Published: 9 November 2016 c Author(s) 2016. CC-BY 3.0 License. Path and site effects deduced from transfrontier internet macroseismic data of two recent M4 earthquakes in NW Europe Koen Van Noten1, Thomas Lecocq1, Christophe Sira2, Klaus-G. Hinzen3 and Thierry 5 Camelbeeck1 1 Royal Observatory of Belgium, Seismology-Gravimetry, Ringlaan 3, B-1180 Brussels, Belgium 2 French Central Seismological Office, University of Strasbourg, Rue René Descartes 5, 67084 Strasbourg Cedex, France 10 3 University of Cologne, Bensberg Erdbebenstation,Vinzenz-Pallotti-Stasse 26, D-51429 Bergisch Gladbach, Germany Correspondance to: Koen Van Noten ([email protected]) Abstract. The online collection of earthquake testimonies in Europe is strongly fragmented across numerous 15 seismological agencies. This paper demonstrates how collecting and merging “Did You Feel It?” (DYFI) institutional macroseismic data strongly improves the quality of real-time intensity maps. Instead of using ZIP code Community Internet Intensity Maps we geocode individual response addresses for location improvement, assign intensities to grouped answers within 100 km2 grid cells, and generate intensity attenuation relations from the grid cell intensities. Grid cell intensity maps are less subjective and illustrate a more homogeneous intensity 20 distribution than the ZIP code intensity maps. Using grid cells for ground motion analysis offers an advanced method for exchanging transfrontier equal-area intensity data without sharing any personal’s information. The applicability of the method is demonstrated on the DYFI responses of two well-felt earthquakes: the 8 September 2011 ML 4.3 (MW 3.7) Goch (Germany) and the 22 May 2015 ML 4.2 (MW 3.7) Ramsgate (UK) earthquakes.
    [Show full text]
  • Long-Term Seismicity in Regions of Present Day Low Seismic Activity: the Example of Western Europe
    Soil Dynamics and Earthquake Engineering 20 (2000) 405±414 www.elsevier.com/locate/soildyn Long-term seismicity in regions of present day low seismic activity: the example of western Europe Thierry Camelbeecka,*, Pierre Alexandrea, Kris Vannestea, Mustapha Meghraouib aRoyal Observatory of Belgium, avenue circulaire 3, B-1180, Brussels, Belgium bEcole et Observatoire des Sciences de la Terre, rue Rene Descartes 5, F-67084 Strasbourg, France Abstract In western Europe, the knowledge of long-term seismicity is based on reliable historical seismicity and covers a time period of less than 700 years. Despite the fact that the seismic activity is considered as low in the region extending from the Lower Rhine Embayment to England, historical information collected recently suggests the occurrence of three earthquakes with magnitude around 6.0 or greater. These events are a source of information for the engineer or the scientist involved in mitigation against large earthquakes. We provide information relevant to this aspect for the Belgian earthquake of September 18, 1692. The severity of the damage described in original sources indicates that its epicentral intensity could be IX (EMS-98 scale) and that the area with intensity VII and greater than VII has at least a mean radius of 45 km. Following relationships between average macroseismic radii and magnitude for earthquakes in stable continental regions, its magnitude Ms is estimated as between 6.0 and 6.5. To extend in time our knowledge of the seismic activity, we conducted paleoseismic investigations in the Roer Graben to address the question of the possible occurrence of large earthquakes with coseismic surface ruptures.
    [Show full text]
  • Newsletter Eefit
    ISSN 0967-859X THE SOCIETY FOR EARTHQUAKE AND S CIVIL ENGINEERING DYNAMICS E SECED E NEWSLETTER Volume 23 No 2 D November 2011 In this issue The following article appeared first inProceedings of the ICE - Forensic EEFIT – the UK Earthquake Engineering (August 2011). It is reproduced with permission. Engineering Field Investigation Team 1 Great East Japan Earthquake: Nuclear accident and lessons in resilience 7 EEFIT Notable Earthquakes April – June 2011 13 The UK Earthquake Engineering Pile design in seismic areas 14 Field Investigation Team Forthcoming events 20 EEFIT report on Haiti earth- quake 20 Edmund Booth Sean Wilkinson Consultant University of Newcastle Robin Spence Matthew Free Tiziana Rossetto Cambridge Architectural Research Ove Arup & Partners University College London University of Cambridge Antecedents of EEFIT Ambraseys studied the Skopje earthquake of 1963 and Field investigations of earthquakes by British engineers and five other events for UNESCO (Ambraseys, Moinfar and scientists have a long history dating back to Robert Mallet Tchalenko, 1986) and his many and significant contribu- (1820 – 1880) and John Milne (1880 – 1940) (Muir Wood, tions to the discipline of engineering seismology drew on 1988). In our own time, Nicholas Ambraseys of Imperial his extensive experience of earthquake field missions. College London was a pioneer in recognizing the value of Other UK engineers, too, were carrying out field mis- field missions in grounding the often abstract discipline sions, and the direct origin of EEFIT lay in an investigation into hard reality. He wrote: of the 1980 earthquake in Irpinia, Italy (Spence et al 1982). The Irpinia mission led to the realization of the value of “There is little room in Engineering Seismology carrying out field investigations as soon as possible after for ‘armchair seismologists’.
    [Show full text]
  • Feldbiss Fault Zone - Roervalley Rift System, the Netherlands), Based on Trenching
    Netherlands Journal of Geosciences / Geologie en Mijnbouw 82 (2): 177-196 (2003) Late Quaternary tectonic evolution and postseismic near surface fault displacements along the Geleen Fault (Feldbiss Fault Zone - RoerValley Rift System, the Netherlands), based on trenching R.F. Houtgasf'1, R.T. van Balen% C. Kassea, & J. Vandenberghe3 a Vrije Universiteit, Faculteit der Aard- en LevensWetenschappen, de Boelelaan 1085, Amsterdam, Netherlands; e-mail: [email protected] ~^k -w- 1 R.F. Houtgast: corresponding author |^k I Manuscript received: May 2002; accepted: January 2003 | Abstract In northwest Europe the pattern of earthquake distribution is correlated with known Quaternary faults. Excavation of fault scarps revealed that these fault zones have been active during the Late Pleistocene. In this paper we present the results of an exploratory trenching study across the Geleen Fault, part of the Feldbiss Fault Zone, the Netherlands. Middle Saalian fluvial deposits of the Meuse, overlain by local slope deposits, were excavated. The Geleen Fault has displaced the fluvial deposits by at least 5 meters. The upper layers of local slope deposits could be correlated across the fault and were all dated at approxi­ mately 15 ka B.P. This gives the opportunity to reconstruct the sequence of events that occurred about 15 ka ago. Liquefac­ tions provide evidence for an earthquake event. However, the main offset along the Geleen Fault is not stratigraphically relat­ ed to the liquefactions. The liquefactions and the fault offset are stratigraphically separated by a period of erosion. We there­ fore propose a sequence of events starting with an earthquake accompanied by liquefaction, followed by a period of postseis­ mic displacement with high rates compared to the long-term average.
    [Show full text]