Ac#ve tectonics and the earthquake cycle

Transcription

1 Ac#ve tectonics and the earthquake cycle Olaf Zielke, KAUST October 9-11, 2017 Potsdam 10/29/17 1

2 About me Diplom at University of Potsdam,-2004 Paleoeismology of Kenya RiL Used trenching and geomorph. mapping and da#ng techniques PhD at Arizona State University, Paleiseismic and tectono-geomorph inves#ga#on along the SAF Numerical modeling of fault behavior over many EQ cycles Post-doc at GFZ Potsdam, Ac#ve tectonics along Atacama fault system and North Anatolian Fault system Research scien#st at KAUST, Kinema#c source inversion Geomorph. offset measurement Numerical rupture simula#ons Topic throughout these different stages has been the recurrence of large, poten#ally destruc#ve earthquakes 10/29/17 2

3 KAUST Currently ~7,000 people on campus, will grow to 20,000 Very interna#onal, open community Offers MS and PhD programs in wide range of natural sciences Great facili#es and research opportuni#es even for interns and visi#ng students KAUST 10/29/17 google maps 3

4 How about you? Background Mo#va#on to a_end the course Specific topics to cover 10/29/17 4

5 EQ cycle studies, mo#va#on Seismic hazard concentrated along plate boundaries In many cases close to large popula#on centers Understanding this hazard is prime mo#va#on to study EQs Giardini et al. (2003) 10/29/17 5

6 Seismic hazard is prime mo#vator Shedlock and Tanner (1999) : ~60% of fatali#es from natural hazards related to catastrophic earthquakes 2016, Amatrice 1999, Izmit 2008, Wenchuan 2004, Sumatra 2011, Tohoku

7 Recurrence characteris#cs of (large) earthquakes When did the last large EQ along the fault occur and how large was it? 1999, Izmit EQ How large is the next earthquake probably going to be? T. Hergert What controls the #ming between successive large earthquakes? What controls the (change in) size of successive large earthquakes? How does it affect seismic hazard? 10/29/17 7

8 Within this course we will be Using methods of ac#ve tectonics to constrain single-earthquake rupture characteris#cs pa_erns in earthquake recurrence, if they exist Methods include interpreta#on of geode#c, stra#graphic, and geomorphic data in this context Goal of this course is to provide comprehensive overview of the tool kit, used to inves#gate earthquakes and their recurrence 10/29/17 8

9 What you ll need Computer with Matlab AgiSoL Photoscan (trial version ok for course) h_p:// CloudCompare (free version) h_p://cloudcompare.org Drawing utensils (e.g., pencils, colored pencils) Ques#ons and drive to ac#vely par#cipate 10/29/17 9

10 Ac#ve tectonics and the earthquake cycle day 1, morning: Concept of EQ cycle & genera#on of high-res. DEMs via SfM 10/29/17 10

11 A piece of Ross Stein s 2016 presenta#on at Oakland speaker series => introduc#on to EQ cycle 10/29/17 11 h_ps://

12 Elas#c rebound theory (Reid, 1910) Alterna#on of slow and steady strain accumula#on (interseismic period) sudden strain release (coseismic period) Plate mo#on con#nues è further strain build-up, thus defining the earthquake cycle 10/29/17 12

13 Elas#c rebound theory Different phases can be represented by spring-slider models Highlights that earthquakes are primarily a fric#onal process No slip as long as applied shear stress is smaller than fric#onal strength Fs=µsσn; τ = 0; No slip if τ < Fs 10/29/17 13

14 Elas#c rebound theory Different phases can be represented by spring-slider models Highlights that earthquakes are primarily a fric#onal process No slip as long as applied shear stress is smaller than fric#onal strength Fs=µsσn; τ > 0; No slip if τ < Fs 10/29/17 14

15 Elas#c rebound theory Different phases can be represented by spring-slider models Highlights that earthquakes are primarily a fric#onal process No slip as long as applied shear stress is smaller than fric#onal strength F s =µ s σ n; τ > F s è slip (strain release) 10/29/17 15

16 Elas#c rebound theory If rate of strain build-up & rate of strain release is are known then we should be able to predict earthquake recurrence This idea is expressed in the characteris#c earthquake model τ1 =sta#c strength, τ2 =dynamic strength 10/29/17 16

17 Parkfield, California Repea#ng ~M6 earthquakes since ~1850s very ~24 years In-between fully locked and creeping sec#ons of the SAF 2004 => ~16years too late 10/29/17 17

18 Nankai trough, Japan Long historical records spanning years Early records only with damage distribu#on 10/29/17 18

19 Nankai trough, Japan For more recent earthquakes, also eleva#on change was recorded Was found that #me to next earthquake was dependent on slip of previous event 10/29/17 19

20 Nankai trough, Japan The conceptual idea: if slip in previous event was large, then it takes longer to rebuild the released amount of stress 10/29/17 20

21 End-member scenarios for EQ recurrence Char. EQ model Time-pred. model Slip-pred. model 10/29/17 21

22 Other models Other recurrence models were based on alongfault slip accumula#on Formulated based on observa#ons along strike-slip and normal faults in the Western US 10/29/17 22

23 Another piece of Ross Stein s 2016 presenta#on at Oakland speaker series 10/29/17 23 h_ps://

24 Elas#c rebound theory EQs are inherently unpredictable because of complex interac#on and poorly constrained boundary condi#ons while the concept of stress renewal is plausible, it is less simple than we may have hoped was men#oned that EQs were not all same size; BUT they were similar in size & not en#rely random s#ll some predictability w/r to future EQ size? Also, historical records indicate existence of recurrence pa_erns 10/29/17 24

25 Elas#c rebound theory even if EQs are not predictable per se (by the day/week/ year); we can s#ll learn about their recurrence by studying current and past earthquakes For example: è Need to inves#gate fault interac#on and mul#-segment rupture probability è Understanding the physical processes of fric#on è Need to inves#gate spa#al and temporal variability in rupturecontrolling parameters (affec#ng e.g., slip along fault) 10/29/17 25

26 Types of data to study current and past EQs Seismic data Seismic moment release Kinema#c rupture models Only current events, recorded by seismographs Historical accounts of past earthquake rupture OLen reasonably good #me informa#on Generally incomplete (only large, destruc#ve EQs) and difficult to a_ribute host fault w/ EQ Stra#graphic data Allow to extend the EQ catalog into past Only surface-rupturing EQs and only as points along the fault Geomorphic data Allow to inves#gate slip accumula#on pa_erns along fault Only surface-rupturing EQs No direct control on #ming of causa#ve EQs 10/29/17 26

27 Types of data to study current and past EQs Seismic data Seismic moment release Kinema#c rupture models Only current events, recorded by seismographs Historical accounts of past earthquake rupture OLen reasonably good #me informa#on Generally incomplete (only large, destruc#ve EQs) and difficult to a_ribute host fault w/ EQ Stra#graphic data Allow to extend the EQ catalog into past Only surface-rupturing EQs and only as points along the fault Geomorphic data Allow to inves#gate slip accumula#on pa_erns along fault Only surface-rupturing EQs No direct control on #ming of causa#ve EQs 10/29/17 27

28 Types of data to study current and past EQs Seismic data Seismic moment release Kinema#c rupture models Only current events, recorded by seismographs Historical accounts of past earthquake rupture OLen reasonably good #me informa#on Generally incomplete (only large, destruc#ve EQs) and difficult to a_ribute host fault w/ EQ Stra#graphic data Allow to extend the EQ catalog into past Only surface-rupturing EQs and only as points along the fault Geomorphic data Allow to inves#gate slip accumula#on pa_erns along fault Only surface-rupturing EQs No direct control on #ming of causa#ve EQs 10/29/17 28

29 Types of data to study current and past EQs Seismic data Seismic moment release Kinema#c rupture models Only current events, recorded by seismographs Historical accounts of past earthquake rupture OLen reasonably good #me informa#on Generally incomplete (only large, destruc#ve EQs) and difficult to a_ribute host fault w/ EQ Stra#graphic data Allow to extend the EQ catalog into past Only surface-rupturing EQs and only as points along the fault Geomorphic data Allow to inves#gate slip accumula#on pa_erns along fault Only surface-rupturing EQs No direct control on #ming of causa#ve EQs 10/29/17 29

30 Types of data to study current and past EQs Seismic data Seismic moment release Kinema#c rupture models Only current events, recorded by seismographs Historical accounts of past earthquake rupture OLen reasonably good #me informa#on Generally incomplete (only large, destruc#ve EQs) and difficult to a_ribute host fault w/ EQ Stra#graphic data Allow to extend the EQ catalog into past Only surface-rupturing EQs and only as points along the fault Geomorphic data Allow to inves#gate slip accumula#on pa_erns along fault Only surface-rupturing EQs No direct control on #ming of causa#ve EQs 10/29/17 30

31 Break Next: High-resolu#on DEM genera#on with SfM approach 10/29/17 31

32 Geomorphic evidence of faul#ng Sufficiently large EQs will disrupt the surface topography Careful analysis of EQ surface ruptures provides informa#on on the physics of the rupture process Surface ruptures, M7.8 Kaikoura EQ 2016 dm to m scale h_ps://

33 h_ps:// Kekerengu alone is 30+ km of this very complex ground rupture (total surface rupture more than 170km long) dm to m scale details ma_er a lot to understand rupture process

34 Scien#fic data requirements Need topography data with sufficient spa#al extent and resolu#on to capture phenomena of interest Need topography data with sufficient temporal repeat to capture changes of interest Surface ruptures, M7.8 Kaikoura EQ 2016 dm to m scale h_ps://

35 High-resolu#on data sets Differen#al GPS Time-consuming, only for local studies feasible LiDAR (terrestrial, airborne) Genera#on of bare-earth DEMs Data acquisi#on not trivial, expensive 10/29/17 35

36 Great resource for data and educa#on 10/29/17 36

37 High-resolu#on data sets Differen#al GPS Time-consuming, only for local studies feasible LiDAR (terrestrial, airborne) Genera#on of bare-earth DEMs Data acquisi#on not trivial, expensive Photogrammetry Classical olen mul#-#me coverage of same loca#on Resolu#on may be too coarse Structure-from-mo#on easy data acquisi#on and stream-lined processing no bare-earth DEMs 10/29/17 37

38 High-resolu#on data sets Differen#al GPS Time-consuming, only for local studies feasible LiDAR (terrestrial, airborne) Genera#on of bare-earth DEMs Data acquisi#on not trivial, expensive Photogrammetry Classical olen mul#-#me coverage of same loca#on Resolu#on may be too coarse Structure-from-mo#on easy data acquisi#on and stream-lined processing no bare-earth DEMs 10/29/17 38

39 Nissen (2016)

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57 Exercise 10/29/17 57