title: Modal investigation of elastic anisotropy in shallow-water environments: anisotropy beyond vertical transverse isotropy.
abstract: Theoretical and numerical results are presented for modal characteristics of the seismo-acoustic wavefield in anisotropic range-independent media. General anisotropy affects the form of the elastic-stiffness tensor, particle-motion polarization, the frequency and angular dispersion curves, and introduces near-degenerate modes. Horizontally polarized particle motion (SH) cannot be ignored when anisotropy is present for low-frequency modes having significant bottom interaction. The seismo-acoustic wavefield has polarizations in all three coordinate directions even in the absence of any scattering or heterogeneity. Even weak anisotropy may have a significant impact on seismo-acoustic wave propagation. Unlike isotropic and transversely isotropic media with a vertical symmetry axis where acoustic signals comprise P-SV modes alone (in the absence of any scattering), tilted TI media allow both quasi-P-SV and quasi-SH modes to carry seismo-acoustic energy. Discrete modes for an anisotropic medium are best described as generalized P-SV-SH modes with polarizations in all three Cartesian directions. Conversion to SH is a loss that will mimic acoustic attenuation. An in-water explosion will excite quasi-SH.
authors.affiliation: Department of Earth and Space Sciences, University of Washington, 63 Johnson Hall, Box 351310, Seattle, Washington 98195, USA.
authors.forename: Darin J
authors.initials: DJ
authors.lastname: Soukup
authors.forename: Robert I
authors.initials: RI
authors.lastname: Odom
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Park