HR: 11:05h
AN: S52A-04    [Abstracts]
TI: Broadband Ground Motion Simulations for the Puente Hills Fault System
AU: * Graves, R W
EM: robert_graves@urscorp.com
AF: URS Corporation, 566 El Dorado St. - 2nd Floor, Pasadena, CA 91101 United States
AB: Recent geologic studies have identified the seismic potential of the Puente Hills fault system. This system is comprised of multiple blind thrust segments, a portion of which ruptured in the M_w 5.9 Whittier-Narrows earthquake. Rupture of the entire system could generate a M_w 7.2 (or larger) earthquake. To assess the potential hazard posed by the fault system, we have simulated the response for several earthquake scenarios. These simulations are unprecedented in scope and scale. Broadband (0-10 Hz) ground motions are computed at 66,000 sites, covering most of the LA metropolitan region. Low frequency (f < 1 Hz) motions are calculated deterministically using a finite-difference approach, which includes a detailed representation of the 3D subsurface structure. High frequency (f > 1 Hz) motions are calculated using a stochastic approach. We consider scenarios ranging from M_w 6.7 to M_w 7.2, including both high and low stress drop events. Finite-fault rupture models for these scenarios are generated following a wavenumber filtering technique (K^-2 model) that has been calibrated against recent earthquakes. In all scenarios, strong rupture directivity channels large amplitude pulses of motion directly into the Los Angeles basin, which then propagate southward as basin surface waves. Typically, the waveforms near downtown Los Angeles are dominated by a strong, concentrated pulse of motion. At Long Beach (across the LA basin from the rupture) the waveforms are dominated by late arriving longer period surface waves. The great density of sites used in the calculation allows the construction of detailed maps of various ground motion parameters (PGA, PGV, SA), as well as full animations of the propagating broadband wave field. Additionally, the broadband time histories are available for use in non-linear response analyses of built structures.
DE: 7209 Earthquake dynamics (1242)
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Seismology [S]
MN: Fall Meeting 2005