HR: 11:20h
AN: S12A-05 [Abstracts]
TI: Evidence for Supershear Rupture During the 1906 San Francisco Earthquake
AU: * Song, S
EM: seisgoo@pangea.stanford.edu
AF: Stanford University, 397 Panama Mall, Stanford, CA 94305
AU: Beroza, G C
EM: beroza@pangea.stanford.edu
AF: Stanford University, 397 Panama Mall, Stanford, CA 94305
AU: Segall, P
EM: segall@pangea.stanford.edu
AF: Stanford University, 397 Panama Mall, Stanford, CA 94305
AB:
The 1906 San Francisco earthquake is perhaps the single most important event in the history of earthquake science.
Measurements taken and analyzed for that event led to the demonstration of elastic rebound. Despite the importance of this
earthquake, the two most recently published source models, one based on seismic data and the other based on geodetic data,
are sharply discordant. We suggest the two source models can be reconciled if rupture in the 1906 earthquake exceeded the
shear wave velocity. Observations of super-shear rupture in recent large strike-slip earthquakes suggests that it is
possible and may even be typical of large strike-slip events. We find that we can fit the geodetic data and the envelope of
the seismic data provided the rupture exceeds the shear wave speed to the north of
Point Arena. We are analyzing non-repeated triangulation measurements and solving the joint slip/rupture velocity inverse
problem to test this hypothesis more rigorously. If supershear rupture in large earthquakes is common, it would be of
fundamental importance for understanding the hazard posed by large strike-slip faults in general, and for our understanding
seismic hazard in northern California in particular, because so much of our characterization of the hazard in that region is
based on our understanding of what
happened in 1906. The prediction of strong ground motion in future large strike-slip earthquakes will be profoundly
different if earthquake rupture velocity is routinely supershear.
DE: 7203 Body waves
DE: 7209 Earthquake dynamics (1242)
DE: 7215 Earthquake source observations (1240)
SC: Seismology [S]
MN: Fall Meeting 2005