Surface wave scattering from 3-D obstacles, Geophys

The scattering of surface waves from 3-D, discrete obstacles in both the near- and far-fields is described using a T-matrix formulation which relates the incident and scattered wavefields via expansions over surface wave modes. The scatterer resides in an otherwise laterally homogeneous, stratified medium and can exhibit an arbitrarily large contrast in material properties with its surroundings. The method relies on the expansion of the incident and scattered wavefields in terms of regular and outgoing surface wave basis functions which depend upon wavetype (Love, Rayleigh), modal order and azimuthal order, and are orthogonal with respect to a specific class of closed surface integral. By expanding the wavefield inside the scatterer in an appropriate set of basis functions, this orthogonality can be exploited to relate the unknown coefficients of the scattered wavefield to those in the known expansion of the incident wavefield via the surface wave T-matrix. This quantity, which depends only on the size and shape of the obstacle, provides a complete description of the scattering response to any incident harmonic wave and permits a broad range of scattering measures (e.g. mode coupling, wavetype conversion