Two-dimensional FM-IBEM solution to the broadband scattering of elastic waves in a fluid-saturated poroelastic half-space

Abstract

The fast multi-pole indirect boundary element method (FM-IBEM) is proposed to efficiently solve the high-frequency and large-scale two-dimensional (2-D) elastic wave scattering in a fluid-saturated poroelastic heterogeneous medium. The diffracted wave fields are constructed by applying virtual distributed loads and fluid sources on the boundaries according to the single-layer potential theory, and the multi-pole moment and local expansion coefficients of 2-D Green's function are deduced based on Graf addition theorem. Numerical results illustrated that the proposed method can essentially reduce the calculation CPU time and the memory requirement. The 2-D scattering of elastic waves by a canyon and a group of cracks in a fluid-saturated poroelastic half-space is further investigated. It shows that the scattering characteristics are closely related to the incident frequency, porosity of the medium and special topography. There is a significant ground motion amplification effect around the canyon, while a group of cracks produce an isolation effect on the half-space surface motion.