Dynamic stress field of a kinematic earthquake source model with k-squared slip distribution

Abstract

Source models such as the k-squared stochastic source model with k-dependent rise time are able to reproduce source complexity commonly observed in earthquake slip inversions. An analysis of the dynamic stress field associated with the slip history prescribed in these kinematic models can indicate possible inconsistencies with physics of faulting. The static stress drop, the strength excess, the breakdown stress drop and critical slip weakening distance Dc distributions are determined in this study for the kinematic k-squared source model with k-dependent rise time. Several studied k-squared models are found to be consistent with the slip weakening friction law along a substantial part of the fault. A new quantity, the stress delay, is introduced to map areas where the yielding criterion of the slip weakening friction is violated. Hisada's slip velocity function is found to be more consistent with the source dynamics than Boxcar, Brune's and Dirac's slip velocity functions. Constant rupture velocities close to the Rayleigh velocity are inconsistent with the k-squared model, because they break the yielding criterion of the slip weakening friction law. The bimodal character of Dc/Dtot frequency - magnitude distribution was found. Dc approaches the final slip Dtot near the edge of both the fault and asperity. We emphasize that both filtering and smoothing routinely applied in slip inversions may have a strong effect on the space-time pattern of the inferred stress field, leading potentially to an oversimplified view of earthquake source dynamics. © 2007 The Authors Journal compilation © 2007 RAS.