A very broad‐band stochastic source model used for near source strong motion prediction

Abstract

The simulation of near‐source ground motion requires the calculation of ground motion in a very broad‐band frequency range (typically from 10 s to 0.1 s). However, the calculation of complete Green's function is too time consuming for high‐frequency simulations. We present a method to obtain very broad‐band synthetic seismograms, combining the kinematic spectral source model of Bernard et al., [1996], and an algorithm, based on the wavenumber technique of Bouchon and Aki, [1977]. High‐frequency radiations are evaluated with ray theory and a broad‐band dislocation defined on a finely discretized fault plane. The low‐frequency radiations due to the near‐ and intermediate‐fields are calculated with the complete field algorithm on a low‐wavenumber filtered dislocation. This dislocation is defined on a coarse grid over the fault, hence significantly reducing the computing time. We apply this method to compute the ground motion at a station located near an extended fault, where the near‐, intermediate‐ and far‐field radiations are important.