Anisotropic effects of non-axial seismic wave propagation in foliated crustal rocks

[1] Seismic wave propagation within the crust is usually in directions not parallel to inherent rock symmetry axes due to geologic dips of structures and/or oblique-to-arcuate raypaths. We use Christoffel equations and petrophysically measured velocities of crustal metamorphic rocks to examine anisotropic velocities and traveltime effects as functions of non-axial propagation. P- and S-wave velocities are trigonometrically weighted between fast and slow axial velocities. Averaging over a range of non-axial angles yields effective velocities as encountered by through-going crustal raypaths. Axial velocities cannot be simply used to quantify crustal anisotropic effects. The angular behavior of P-wave delay and shear wave splitting are sensitive to V-P measured diagonal to the material symmetry axes; this diagonal velocity controls the presence or absence of non-axial shear wave singularities. These behavior help quantify the contributions of crustal rocks to observations of seismic anisotropy which can serve as proxies for crustal deformation.