Scattering from targets in three-dimensional littoral and surf-zone environments with multi-layered elastic sediments based on an interior-transmission formulation

We present a new numerical approach to compute the three-dimensional scattering of acoustic and elastic waves from elastic objects buried in multi-layered elastic sediments. We use a frequency-domain approach and utilize an elastodynamics formulation based on an interior-transmission representation of the scattering problem. This enables us to use the perfectly-matched-layer approximation (PML) method for exterior truncation while avoiding some fundamental problems associated with the truncation of the non-homogeneous exterior domains with coupled elasto-acoustics. We present several examples that verify the new formulation and its finite-element-based numerical implementation. We also demonstrate its application to important problems involving the computation of scattered fields from buried elastic objects buried in littoral or surf-zone domains with a multi-layered sediment modeled as three-dimensional visco-elastic material.