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Repeating Earthquakes: Observations & Interpretations Across Fault Zones

Review and examples of repeating earthquake observations and interpretations, application in various zones, waveforms analysis, moment release distribution, uncertainties in P-wave picks and velocity models. Study of seismic slip activities and stress drops.

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Repeating Earthquakes: Observations & Interpretations Across Fault Zones

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  1. RepeatingEarthquakes Olivier Lengliné - IPGS Strasbourg Cargeseschool

  2. Pleaseinterrupt Questions / remarks

  3. 1 – Review of Repeatingearthquake observations & interpretations 2 – Twoexamples of application

  4. Observations - Waveforms Nadeau & Johnson, 1998

  5. Parkfield, California – Mw6.0 De Bilt, The Netherlands USGS Bakun et al., 2005

  6. Off Kamaishi, Japan – M4.9 Time (s) Uchida et al., 2012

  7. Chihshang fault, Taiwan Chen et al., 2008

  8. Soultz-Sous-Forêts geothermal reservoir, France 9 events 9 events 13 events BRGM 19 events Time (s)

  9. San-Andreas Fault Rubinstein et al., 2012 Schaff & Beroza, 1998

  10. u(t) = Source * Path* Station

  11. u(t) = Source * Path* Station

  12. u(t) = Source * Path* Station Station is the same Change in medium property, [e.gPoupinet et al., 1984] Change in source properties, [e.g. Lengliné & Got, 2011]

  13. Lengliné and Got, 2011 Directivity Velocity variations Poupinet et al., 1984

  14. u(t) = Source * Path* Station Homogeneous medium  waveformsimilarity Station the same Change in medium property, [e.gPoupinet et al., 1984] Change in source properties, [e.g. Lengliné & Got, 2011] !

  15. Observations - Locations Waldhauser et al., 2004

  16. Parkfield Murray & Langbein, 2006

  17. Off Kamaishi Moment release distribution Relative moment releasednormalized by each maximum value Okadaet al., 2002

  18. Earthquake relative relocation • Uncertainties P-wavepicks • Uncertainties of the velocity model

  19. Earthquake relative relocation • Uncertainties P-wavepicks • Uncertainties of the velocity model • More precise data: time delaysestimatedfrom cross-correlation • Ray geometry – rotation • Do not correct absolute position

  20. Earthquake relative relocation • Uncertainties P-wavepicks • Uncertainties of the velocity model • More precise data: time delaysestimatedfrom cross-correlation • Ray geometry – rotation • Do not correct absolute position • From cross-correlation centroid location • Got et al., 1994 • Waldhauser & Ellsworth, 2000

  21. Earthquake relative relocation • Uncertainties P-wavepicks • Uncertainties of the velocity model • More precise data: time delaysestimatedfrom cross-correlation • Ray geometry – rotation • Do not correct absolute position • From cross-correlation centroid location • Got et al., 1994 • Waldhauser & Ellsworth, 2000 • See Tutorial thisafternoon for Methods

  22. Lengliné & Marsan, 2008 Size = Assumed stress drop + circular crack + moment – magnitude relation

  23. Taiwan Soultz-sous-Forêts Bourouis & Bernard, 2007 Radius estimatedfrom corner frequency Chen et al., 2008

  24. Murray & Langbein, 2006 Clusters of co-located, similarwaveformsearthquakes, appearsat the transition betweenfullylocked and fullycreeping areas Rau et al., 2007

  25. ExamplefromNorthern-California Parkfield Waldhauser & Schaff, 2008 Is itrelated to fault slip velocity ?

  26. San Andreas Fault Rubin et al., 1999 Streaks of microearthquakes – along slip direction Rheological/ frictional/ geological / geometrical transition ?

  27. Observations - Timing

  28. Parkfield Earthquakenumber Time (years) μΔt = 24.5 yrσΔt = 9.5 yr COV = 0.37

  29. Repeaters off Kamaishi Repeatinginterval = 5.35 +/- 0.5 yrs Time (years)

  30. San-Andreas faultatParkfield Year Distance alongstrike (km) Waldhauser et al., 2004

  31. Periodicrepeating ruptures Year Distance alongstrike (km) Waldhauser et al., 2004

  32. Rubinstein et al., 2012 Quasi-periodicbehavior of the slip activity

  33. The simplest model Aseismic slip No interactingasperity A lockedseismic patch embedded in a fullycreeping zone

  34. Slip on the creeping part Slip on the seismicasperity Slip Time

  35. Aseismic slip on the fault = seismic slip dseis Slip Time

  36. Aseismic slip on the fault = seismic slip • Elastic solution for a circular crack

  37. Aseismic slip on the fault = seismic slip • Elastic solution for a circular crack

  38. Aseismic slip on the fault = seismic slip • Elastic solution for a circular crack • Constant stress drop

  39. Chen et al., 2007

  40. 1st Hypothesis The constant stress drop hypothesisis not correct Empirical fit to the data thensuggests in order to have Tr ~ M01/6 Impliesthat the stress-drop ishigherfor smallevents. Stress levelsreach 2 GPafor the smallestevents(more than 10 times laboratorystrength) This resultisatoddswithestimatesbased on seismicspectra Relation not consistent withestablishedscaling relations for large earthquakes.

  41. Imanishi & Ellsworth, 2006

  42. Chen & Lapusta, 2009 Chen & Lapusta, 2009

  43. But not the estimated plate velocity – streaks close to locked section  reducedvelocity ?

  44. Slip on the creeping part Slip on the seismicasperity Slip Time Seismic slip

  45. Off KamaishirepeatingsequencefollowingTohoku, 2011, Mw9 earthquake Uchida, 2014

  46. Lengliné & Marsan 2008 Schaff & Beroza, 1998

  47. FollowingParkfield, 2004, Mw6 event

  48. Response of a velocitystrengthening area to a stress-step Marone, 1991 The Omorilikedecay of RES iswellrendered by the slip evolution of the creeping area following a stress step

  49. Nadeau & McEvilly, 1999

  50. Nadeau & McEvilly, 1999

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