La dynamique des tremblements de terre vue à travers le séisme de Landers du 28 juin 1992

Abstract

We study the influence of initial conditions and of friction laws on the propagation of dynamic rupture during the earthquake of 28 June 1992 in Landers, California. We model this earthquake solving the elastodynamic wave equation by a finite difference method and we model observed accelerograms in order to get a better knowledge of the dynamic rupture process of this earthquake. In our model rupture propagates spontaneously under the simultaneous control of the initial stress field and friction. We model friction by a simple slip-weakening law. Finally, we inverted the initial stress field and the friction law from the radiation produced by 1992 Landers earthquake using a trial-and-error method. The dynamic model obtained by trial-and-error inversion provides a very satisfactory fit between synthetics and strong motion data. Rupture history and duration of the Landers earthquake are in good agreement with previous kinematic inversion results, without introducing major changes in final slip distribution on the fault. The solution of the dynamic inverse problem is non-unique because this problem is intrinsically ill-posed. Two complementary mechanical models were inverted in order to model the Landers earthquake, and to reproduce the seismic data. The first model corresponds to the asperity model in which only initial stress distribution is heterogeneous. The second model is a barrier model in which the initial stress was perfectly uniform while rupture resistance was heterogeneous. To cite this article: S. Peyrat et al., C. R. Mecanique 330 (2002) 235–248.