ANALYSIS OF THE SH WAVE FIELD IN A HALF SPACE BY THE BOUNDARY ELEMENT METHOD.

An analytical method for calculating the two-dimensional scattering of incident SH waves by surface and near-surface inhomogeneities in a half-space is presented. In order to apply the fundamental solution in an infinite space to the elastodynamic problems in a half-space, the authors propose a method of replacing an infinite stress-free boundary in a half-space by a truncated boundary of finite length. On the basis of the indirect boundary element method formulation, the effective length of the stress-free boundary is determined. The feasibility of this method is investigated by solving the problems of out-of-plane shear wave (SH wave) fields. Then, the topographic effect of shallow tunnels, canyons, and trenches are investigated. The results obtained are in reasonable agreement with those obtained by other methods. Consequently, the proposed method shows great promise for the study of in-plane wave (P and SV wave) fields in a half-space. The authors also discuss the frequency responses of shallow tunnels, canyons, and trenches, and show the applicability of the present method to earthquake engineering.