Scattering of seismic waves by cracks in multi-layered geological regions II. Numerical results

The mechanical model for plane strain, time-harmonic seismic wave propagati on problems in cracked, multi-layered geological regions with surface topog raphy and non-parallel interfaces was described in the first part of this w ork. Here, this model is used to investigate the response of such a region to the presence of traveling elastic waves generated by a seismic source. T he computational methodology that was developed in the first part is based on a combination of both the regular (displacement-based) and the hypersing ular (traction-based) Boundary Integral Equation Method (BIEM). First, the accuracy and convergence characteristics of this hybrid BIEM are studied. T hen, a series of problems involving four different configurations of a refe rence geological deposit with both interface and internal cracks are solved , for a loading that is due to a seismically-induced pressure wave propagat ing upwards from the underlying rigid half-plane. The purpose of the numeri cal study is to investigate the influence of various key parameters of the problem, such as frequency and incidence angle of the incoming wave, size o f the surface relief, location and size of the buried cracks, interaction e ffects between cracks and finally the presence of layers, on both the scatt ered displacement field and the stress concentration field. (C) 2001 Elsevi er Science Ltd. All rights reserved.