HR: 12:05h
AN: S11H-08    [PDF]
TI: Could a Complex Earthquake like the 2002 Denali Fault Event hit the Los Angeles area?
AU: * Anderson, G
EM: ganderson@usgs.gov
AF: U.S. Geological Survey, 525 South Wilson Avenue, Pasadena, CA 91106-3212 United States
AU: Aagaard, B
EM: baagaard@usgs.gov
AF: U.S. Geological Survey, 525 South Wilson Avenue, Pasadena, CA 91106-3212 United States
AU: Hudnut, K
EM: hudnut@usgs.gov
AF: U.S. Geological Survey, 525 South Wilson Avenue, Pasadena, CA 91106-3212 United States
AB: The Denali Fault earthquake sequence began with the 23 October 2002 Mw6.7 Nenana Mountain foreshock, followed on 3 November 2002 by the Mw7.9 Denali Fault mainshock. The mainshock demonstrated that rupture of secondary thrust faults can trigger nearby strike-slip faults, highlighting the possibility that such dangerous earthquakes could occur in more densely populated regions with similar tectonics. For example, previous workers [Eberhart-Phillips \textit{et al., Science,} 2003] have suggested that an earthquake similar to the Denali Fault mainshock could occur in the Los Angeles metropolitan region, home to more than 13 million people. We have tested this proposal by modeling static and dynamic stress interactions between the Sierra Madre-Cucamonga thrust and San Andreas/San Jacinto strike-slip fault systems near Los Angeles. We find that the comparison with the Denali Fault mainshock breaks down due to differences in background stress and fault geometry. In particular, rupture of the Sierra Madre-Cucamonga system is unlikely to trigger rupture of either the San Andreas or San Jacinto fault, as the Susitna Glacier fault triggered the Denali fault during the 2002 event. However, our modeling suggests that under rare circumstances, a large earthquake on the northern San Jacinto fault could trigger a cascading rupture of the Sierra Madre-Cucamonga system, potentially growing into a dangerous Mw7.5--7.8 earthquake on the edge of the heavily populated Los Angeles metropolitan region.
DE: 7209 Earthquake dynamics and mechanics
DE: 7230 Seismicity and seismotectonics
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2003 Fall Meeting