AMPLIFICATION OF SH-WAVES BY AN ORTHOTROPIC BASIN

Scattering of elastic waves by an orthotropic sedimentary basin is inv estigated for antiplane strain model using an indirect boundary integr al equation approach. Both steady state and transient response were ob tained for semicircular and semielliptical basins with different mater ial properties. The results indicate that the basin geometry and the i mpedance contrast between the half-space and the basin have similar ef fects on the surface ground motion amplification as for the isotropic case. However, the material anisotropy may change significantly the fu ndamental resonant frequencies of the basin, resulting in different su rface displacement amplification patterns. In addition, it was observe d that the arrival time of the main disturbance on the surface strongl y depends on material anisotropy for different angles of incidence. Th e results demonstrate that material anisotropy may be very important i n explaining surface ground motion amplification for sedimentary basin s. (C) 1998 John Wiley & Sons, Ltd.