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Rock mechanics view of a seismogenic fault zone. Scholz, 1988. Large shallow earthquakes well imaged by space geodesy. M w 7.3 Landers (California, USA), 1992 M w 7.4 Izmit (Turkey), 1999 M w 7.1 Hector Mine (California, USA), 1999 M w 6.6 Bam (Iran), 2003
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Rock mechanics view of a seismogenic fault zone Scholz, 1988
Large shallow earthquakes well imaged by space geodesy • Mw 7.3 Landers (California, USA), 1992 • Mw 7.4 Izmit (Turkey), 1999 • Mw 7.1 Hector Mine (California, USA), 1999 • Mw 6.6 Bam (Iran), 2003 • Mw 7.9 Wenchuan (China), 2008 • Mw 7.0 Haiti, 2010 • Mw 7.2 El Mayor-Cucapah (Mexico), 2010
M7.3 Landers, 1992 vertical horizontal Fialko et al., JGR 2004
Mw 7.1 Hector Mine (California, USA), 1999 vertical horizontal Fialko et al., GRL 2001 Simons et al., BSSA 2002
Mw 6.6 Bam (Iran), 2003 vertical horizontal Fialko et al., Nature 2005
April 4, 2010 M7.2 El Mayor (Mexico) earthquake ENVISAT track 84 ENVISAT track 77 from ENVISAT and ALOS data
triggered slip Wei et al., 2010
Effect of a fault damage zone Chester et al., 1993 Chester et al., 2005
Effect of a fault damage zone co-Hector Mine Fialko et al., Science, 2002 co-Landers Fialko, JGR 2004
Effect of a fault damage zone Sylvain Barbot Barbot et al., JGR 2008
Conclusions • - Inversions of space geodetic data for slip distribution due to large strike-slip earthquakes reveal “shallow slip deficit” • - Reduced near-surface coseismic slip is predicted by models of earthquake cycle on faults with rate-and-state friction; same simulations predict shallow fault creep in the postseismic and interseismic periods • InSAR observations do not reveal shallow creep sufficient to relieve the inferred coseismic deficit • In the presence of macroscopic compliant zones, the inferred deficit is in fact underestimated • Plastic yielding during coseismic slip tempers strain near the fault and may account for at least some of the deficit