Random Source Effects on Seismic Ground Motions

Abstract

The effect of randomness in the rapture process at the source on the near‐field seismic ground motions is examined. Time histories and response spectra are determined at an observation point in the vicinity of a vertical, strike‐slip fault. The seismic motions resulting from a deterministic, kinematic source model with uniform slip are compared with the motions obtained from stochastic models, in which the rupture parameters vary randomly along the length of the fault. The analysis shows that the random variability in the source parameters (namely, the dislocation amplitude, the rise time, the rupture velocity, and the fault width) enriches the frequency content of the motions. When the random variability in each rupture parameter is investigated separately, it is found that randomness in the rise time and the rupture velocity enhances the frequency content of the motions, whereas the variation in the dislocation amplitude and the fault width produces motions similar to the deterministic ones.