Simulation of Near-Source Ground Motions with Dynamic Failure

We simulate long-period near-source ground motions due to hypothetical events on a strike-slip fault (M_W 6.9) and a buried thrust fault (M_W 7.0). We include the dynamics of the rupture process using a model of sliding friction. The directivity of the rupture creates large displacement and velocity pulses in the ground motions in the forward direction. For the strike-slip fault the peak values occur near the tip of the fault, while for the buried thrust fault the peak values occur up-dip from the top of the fault. The acceleration response spectra in the 2.0 sec to 3.0 sec range exceed 1.0 g near the strike-slip fault in the forward direction, and 0.5 g up-dip from the top of the thrust fault. These results quantify the threat posed to long-period structures near faults.