Dynamic propagation of shear dislocations applied to seismic models

Abstract

Two analytical approaches based on the methods of self-similar potentials and rotational superposition are developed for the study of three-dimensional dislocation source models for earthquakes. The first approach deals with the sudden stopping of a spreading circular shear dislocation. The second approach is an extension of the usual rotational superposition by including a stretching effect, which leads to the solution of problems such as the propagation of an elliptical shear dislocation.

The combined use of these two techniques permits an analytical solution for the problem of an elliptical shear dislocation that expands on a plane in an elastic unbounded medium and then suddenly stops. These results for a full space are then used as the incident waves for studies of the same dislocation source in a homogeneous half space and in a layered half space. In these problems, the subsurface fault plane and any interface between layers are taken parallel to the surface.

The induced motions are shown to change considerably if the sudden stopping is included in the dislocation model. As expected, a layered structure of the medium influences the character of the surface response significantly. The results suggest that intermittent faulting processes as well as local geology must be taken into account in the development of a reasonable earthquake source model.