Scattering Of Elastic Waves By A Three-dimensional Canyon Or Alluvial Valley In Transversely Isotropic Layered Half-space

The seismic response research of complex local site is a hot topic in earthquake engineering,seismology and geophysics.However,most researches only focus on the assumed isotropic medium,with few works devoted to taking anisotropic medium into account.In fact,the natural soil shows obvious anisotropy due to weathering and sedimentation.Therefore,introducing transversal isotropy(TI)medium into the seismic response research is of great significance in both theory and practical application.Based on the indirect boundary element method(IBEM,)this paper studies the scattering problem for canyon and alluvial valley in three-dimensional(3D)TI layered half-space.The main works are as follows:1.Based on the stiffness matrix for TI layered half-space,the Green's function for uniformly-distributed inclined plane load is derived.The correctness of Green's function is verified,and the results of Green's function are given in both frequency and time domain,and related factors are analyzed.2.With the stiffness matrix and Green's function,the IBEM is used to inspect the scattering problems for a canyon under the plane waves(qP-,qSV-and SH-wave).The inerrancy of the method is verified,and numerical examples for homogeneous half-space and a single layer overlying the bedrock are given.Analysis is carried out in frequency domain,and influencing factors,such as TI parameters,incident wave type,incidence angle and the incident frequency,are discussed in detail.3.On the basis of the research about scattering problems for a canyon,the IBEM is expanded to solve the scattering problems for an alluvial valley under the plane waves.With the verified correctness of the method,numerical examples for homogeneous half-space and a single layer overlying the bedrock are given.Analysis is carried out in frequency domain,and factors related to the results are discussed.Research shows that,the existence of complex local site has obvious effects on the displacement amplitude.And the results are closely related to factors such as the type of incident waves,incident angle and the site condition.Most importantly,under the same conditions,the dynamic response of TI site shows significant difference with that of an isotropic site.