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Lingsen Meng, Jean-Paul Ampuero, Morgan Page, Ken Hudnut

SEISMOLOGICAL EVIDENCE AND DYNAMIC MODELING OF REVERSE RUPTURE PROPAGATION DURING THE 2010 MW 7.2 EL MAYOR - CUCAPAH EARTHQUAKE. Lingsen Meng, Jean-Paul Ampuero, Morgan Page, Ken Hudnut. Seismo Lab California Institute of Technology. COMPLEXITY OF DYNAMIC RUPTURE.

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Lingsen Meng, Jean-Paul Ampuero, Morgan Page, Ken Hudnut

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  1. SEISMOLOGICAL EVIDENCE AND DYNAMIC MODELING OF REVERSE RUPTURE PROPAGATION DURING THE 2010 MW 7.2 EL MAYOR - CUCAPAH EARTHQUAKE Lingsen Meng, Jean-Paul Ampuero, Morgan Page, Ken Hudnut Seismo Lab California Institute of Technology

  2. COMPLEXITY OF DYNAMIC RUPTURE Ripperger, Ampuero, Mai (2008) Complicated rupture patterns emerge in dynamic simulations: variable rupture speed, isolated front, frequency dependent behaviors High frequency hard to see in traditional source inversions based on seismic/geodetic observations (<1Hz)

  3. 2010 EL MAYOR - CUPACAH EARTHQUAKE (Wei et al,2011)

  4. Eyewitness account byRosario García González,elder of the Comunidad Cucapah Indígena • Shaking before surface rupture • Reverse rupture direction (Conducted by Ken Hudnut)

  5. Earthquake source imaging by back-projection of array data • The idea is to stack over different moveouts to recover source locations. (Hutko, 2009) • Benefits : • No assumptions of prior rupture kinematics and geometry • High frequency aspect of the rupture is complementary to low frequency( finite fault model) 2004 Sumatra earthquake (Ishii et al, 2005)

  6. IMAGING EL MAYOR-CUPACAH EVENT BY USARRAY & SIEDCAR ARRAY • SIEDCAR array at Rio Grande Rift • Distance 7 ° ~ 12 ° • USarray:40 stations • SIEDCAR:60 stations • Oriented 50 ° from Fault strike • Targeting California fault systems

  7. SYNTHETIC SCENARIOS Slip model with theoretical Green’s function Reverse rupture with empirical Green’s function • Imaging the strongest asperities • Prominent features repeat in arrivals and codas • Capable of reproducing reverse propagation with realisitic Green’s function

  8. SEISMOLOGICAL EVIDENCE OF REVERSE RUPTURE • Bilateral rupture with reverse propagation in the north • Rupture features show up twice as expected from synthetic tests • Result of both arrays are mutually consistent SE NW

  9. SIMILARITY TO 1984 MORGAN HILL EARTHQUAKE • directivity effect of phases at different stations • A asperity first resisted to fail, but eventually ruptured inward and slip massively (Beroza & Spudich,1988)

  10. DYNAMIC RUPTURE MODELS Yield stress • Dynamic triggering of detached asperity • Later break of shallower barrier Slip velocity SE NW Accumulatedslip (Dynamic simulation conducted by Morgan Page)

  11. SHALLOW BARRIER FROM GEOMETRICAL FAULT COMPLEXITY Flower structures in strike slip tectonics (Fletcher et al)

  12. SUMMARY • Reverse rupture supported from both eye witness account and regional seismic back projection. • Later break of shallow barrier (geometrical complexity) is a dynamically plausible interpretation SE NW

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