A Review of Seismic Anisotropy

Lithosphere is usually modeled as a layered isotropic medium. However, in reality, upper mantle is anisotropic as evidenced by the azimuthal dependence of P and S wave propagation speed. Probable causes of the observed seismic wave propagation anisotropy include the aligned crystal structure of minerals, aligned cracks and fractures. This anisotropy in the lithosphere has been greatly studied in terms of shear wave splitting, Love/Rayleigh wave incompatibility, azimuthal dependence Pn velocities (Anderson, 1989). Adequate knowledge of the deviation of deformation from the isotropic layer assumption under different boundary conditions will help explain the observed deformation of the lithosphere. The elastic stiffness tensor changes with crystal symmetry representing or associated with a given seismic anisotropy. I am going to use the stiffness tensor for different types of crystal symmetry and will investigate the changes in the deformation patterns of models with different crystal symmetry under different orientation of applied loading. The purpose of this term project is to review previous works in seismic anisotropy and its various applications in Earth’s science.