lingsen meng, jean-paul ampuero, morgan page, ken hudnut
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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 LabCalifornia Institute of Technology
COMPLEXITY OF DYNAMIC RUPTURE
• 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)
Ripperger, Ampuero, Mai (2008)
2010 EL MAYOR - CUPACAH EARTHQUAKE
(Wei et al,2011)
Eyewitness account byRosario García González,
elder of the Comunidad Cucapah Indígena
(Conducted by Ken Hudnut)
• Shaking before surface rupture
• Reverse rupture direction
(Hutko, 2009)
EARTHQUAKE SOURCE IMAGING BY BACK-
PROJECTION OF ARRAY DATA
2004 Sumatra earthquake (Ishii et al, 2005)
The idea is to stack over different moveouts to recover source locations.
Benefits :No assumptions of prior rupture kinematics and geometry
High frequency aspect of the rupture is complementary to low frequency( finite fault model)
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
• Imaging the strongest asperities• Prominent features repeat in arrivals and codas• Capable of reproducing reverse propagation with realisitic
Green’s function
SYNTHETIC SCENARIOSSlip model with theoretical
Green’s functionReverse rupture with
empirical Green’s function
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
NWSE
SIMILARITY TO 1984 MORGAN HILL EARTHQUAKE
(Beroza & Spudich,1988)
• directivity effect of phases at different stations
• A asperity first resisted to fail, but eventually ruptured inward and slip massively
1. Dynamic triggering of detached asperity2. Later break of shallower barrier
NWSE
DYNAMIC RUPTURE MODELS
Yiel
d st
ress
Slip
vel
ocity
Accu
mul
ated
slip
(Dynamic simulation conducted by Morgan Page)
SHALLOW BARRIER FROM GEOMETRICAL FAULT COMPLEXITY
(Fletcher et al)
Flower structures in strike slip tectonics
SUMMARY
NWSE
• 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
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