Abstract:In this paper, a fast broadband indirect boundary element method is developed for the scattering of spherical waves in a three-dimensional half-space local site. The solution model is established by using ANSYS, and the corresponding program is compiled based on the Intel Fortran compiler. The scattering of spherical waves by three-dimensional semi-ellipsoidal basin is studied numerically, and the influence of some parameters, i.e., the frequency of incident wave, the depth of wave source, and the distance between wave source and sedimentary basin on the ground motion characteristics, were discussed in detail. The calculation method was suitable for solving local surfaces with arbitrary complex shapes, and the fine solution in the frequency domain of the 3D seismic response of a sedimentary basin was realized. Results show that the magnification and interference effect of the sedimentary basin increase with the increase in the incident wave frequency. Under the incident high-frequency wave, the displacement in the secondary direction has a certain edge effect due to the superposition of the body wave transmitted from the bottom of the basin, the surface wave converted from the body wave inside the basin, and the body wave transmitted from the edge of the basin. The analysis of displacement spectrum showed that at a low frequency, the principal displacement amplitude of different points on the surface is basically the same; in the high-frequency domain, the displacement spectrum characteristics of different surface locations are different. Compared with the plane wave incident, the displacement amplitude decreases somewhat. On the whole, as the horizontal distance between the expansion wave source and the basin increases, the maximum displacement amplitude in the main direction of the surface decreases, and the displacement focus area in the subsurface direction increases and the distribution is more dispersed.
