Forward prediction model of earthquake ground motion in sedimentary basins for seismic design of structures

采用直接三维边界元法对三维沉积盆地中入射SH、P、SV和Rayleigh波进行了地震波评价。我们对弹性半空间介质使用了格林函数。由于弹性介质自由表面的边界条件是自动满足的，因此可以根据任意形状的土体界面边界条件，通过格林函数精确地推导出直接三维边界元法。半球形沉积盆地非垂直传播SH波的地表位移振幅的数值结果与基于波函数展开和方位角分解的解（Sanchez-Sesma et al., 1989）的结果很好地吻合。值得注意的是，该方法不仅适用于入射体波的散射，也适用于入射面波的散射，因为它是用满足半空间表面自由边界条件的精确格林函数来表示的边界元问题。

A direct 3-D boundary element method is applied to evaluate seismic waves in three dimensional sedimentary basin for incident SH, P, SV, and Rayleigh waves. We have utilized the Green's functions for an elastic half-space medium. Since the boundary conditions at the free surface of elastic media are automatically satisfied, the direct 3-D boundary element method is precisely formulated through those Green's functions based on the boundary conditions along a arbitrarily shaped soil interface. Numerical results of surface displacement amplitudes of a semi-spherical sedimentary basin for SH waves propagating nonvertically to the surface show good agreements with those results evaluated with the solution(Sanchez-Sesma et al., 1989)based on wave function expansions and an azimuthal decomposition. It should be noted that the present method is applicable to the scattering of not only incident body waves but also incident surface waves by a 3-D sedimentary basin whose soil interface is arbitrarily shaped, because a boundary element problem is formulated in terms of exact Green's functions which satisfy the free-boundary conditions on the half-space surface.