| The local sites have important effects on seismic wave propagation. According to the precious investigation of earthquake damage, local topography has significant amplification on seismic action. The study for Scattering of elastic waves by local sites have became an important research topic in many fields, e.g. Seismology, Earthquake Engineering and Soil dynamic, etc. A hybrid technique(FEM-IBIEM) is developed for studying scattering of seismic waves by a complex local site. Comparing with the domain discretization method, in the aspect of elastic wave exact solution problems, the boundary element method(BEM) has unique advantages in reducing the dimensions of problem solving, decreasing the calculation of degrees of freedom greatly for the 3D issues. For the local site with complex material and geometric features, FEM is more convenient.Sedimentary valley has significant amplification effect on ground motion,and the existence of the soft interlayer has a large influence on the amplification effect. The seismic response of layered sedimentary valley containing soft interlayer under P,SV and Rayleigh waves incidence is calculated and analyzed by a highly accurate finite element- indirect boundary integral coupling method. Numerical results illustrate that the influence features of the soft interlayer on the ground motion of the valley strongly depend on the incident frequency and angle, soft layer’s thickness and buried depth. On the whole, As for the earthquake displacement amplitude, soft interlayer has a large amplification effect which seems more obvious for low frequency waves and the thick soft layer with shallow depth; while for high frequency waves, the effect of vibration reduction may be more dominant. As for the ground surface acceleration, the soft interlayer mainly shows deamplification effect, which can be up to 30%. In Addition, the effect of soft interlayer seems more significant for P waves incidence than that of SV waves incidence.Local site linear analysis of the seismic wave scattering is of important theoretical significance, to suit the actual site, This article has analyzed the nonlinear seismic response of two-dimensional sedimentary valley, based on two dimensional strain state space theory and using the equivalent linearization method. The half space using IBIEM, while Sedimentary internal using equivalent linearization method, iterative update with equivalent shear modulus and damping ratio. This method is easy to deal with different incident wave, incident Angle, the effects of space shape, material, etc. Input the Tar-tarzana wave, we can get the acceleration time history curve and response spectrum, compared with the acceleration time history of corresponding elastic, then some useful conclusions are drawn.A hybrid technique(FEM-IBIEM) is used for studying scattering of seismic waves by a 3-D complex local site. Indirect boundary integral equation method(IBIEM) adopts the dynamic Green’s functions of concentrated loads for a layered half space. It can satisfy the radiation condition of waves in semi-infinite layered media accurately and reduce the computational memory greatly. Based on accuracy tests and taking the seismic wave scattering resulting from three dimensional sedimentary basins and mountains as the example, the adaptability of the proposed method for the seismic response in the complex local site is conformed, and several beneficial conclusions about the three-dimensional sedimentary basin effects and mountain vibration are drawn. This method can be used for studying scattering of elastic waves by arbitrary inhomogeneous site in layered half-space. |
PDF Full Text Request