HEAD WAVE CONTRIBUTIONS TO ELASTIC WAVE FIELDS IN A TRANSVERSELY ISOTROPIC HALF-SPACE

Abstract

Previous studies of the epicentral motion of a linear, transversely isotropic, elastic half-space, subjected to a point force, have provided detailed knowledge of the time dependence of the axial displacement for the case when the zonal axis of the medium coincides with the normal to the stress-free surface (1, 2). Such time dependence varies significantly with the values of the elastic parameters and some features are here shown to be occasioned by head wave contributions. The specification of head waves in anisotropic media is shown to be dependent on simple geometrical constructions in slowness space, previously presented in slightly different form by Willis and Bedding (8). Detailed examples for cases which arise in the symmetric, transversely isotropic problem are presented. Criteria which determine whether head waves contribute to the axial displacement are established.