HR: 1340h
AN: S13D-1084    [Abstracts]
TI: The Influence of the Geometry of the San Andreas Fault System on Earthquakes in California
AU: * Li, Q
EM: qlpkd@mizzou.edu
AF: University of Missouri-Columbia, 101 Geology Building, MU, Columbia, MO 65211 United States
AU: Liu, M
EM: lium@missouri.edu
AF: University of Missouri-Columbia, 101 Geology Building, MU, Columbia, MO 65211 United States
AB: The San Andreas Fault is believed to be the main surface trace of the plate boundary between the North American and the Pacific plates. From 1800 to present, three large historical earthquakes (1857 M7.9, 1906 M8.25, and 1989 M7.1) ruptured the San Andreas Fault. At the same time, more than a dozen M$>$7.0 earthquakes occurred outside the main trace of the San Andreas Fault. Most of the off-main-trace large earthquakes were scattered in Southern California, whereas in northern and central California, earthquakes were clustered along the main trace of the San Andreas Fault. Such a seismic distribution may be related to the geometry of the San Andreas Fault, which is curved with a major bending in southern California. In this study, we constructed a finite element model to explore the influence of the geometry of the San Andreas Fault system on stress distribution and seismicity in California. In the model, the San Andreas Fault is simulated with a weak zone that obeys the Coulomb Friction Law. The model results show that along relative straight segments of the San Andreas Fault in northern and central California, fault slip on the main fault trace causes low level stresses in nearby regions. Along the bended San Andreas Fault in southern California, however, the relative plate motion causes significant off-main-trace stress buildup, consistent with the distribution of large historical earthquakes outside the San Andreas Fault.
DE: 7230 Seismicity and seismotectonics
DE: 7260 Theory and modeling
DE: 7200 SEISMOLOGY
DE: 7209 Earthquake dynamics and mechanics
SC: Seismology [S]
MN: 2004 AGU Fall Meeting