Broadband ground motion simulations for scenario ruptures of the Puente Hills fault

As a first step towards assessing the potential ground shaking hazard posed by the Puente Hills fault system, we have simulated the response for several earthquake scenarios. These simulations are unprecedented in scope and scale. For each scenario, we compute broadband (0-10 Hz) ground motion time histories at 66,000 sites, covering most of the Los Angeles metropolitan region. We consider three scenarios ranging from M _w 6.7 to M _w 7.2. 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, as well as animations of the propagating broadband wave field.