Azimuthal Variation in the Surface-Wave Velocity in the Arabian Plate

Abstract

This pioneer study determined the azimuthal variation in surface-wave fundamental-mode phase velocity for the Arabian plate, concluding that this variation is not due to seismic anisotropy but to lateral heterogeneity, which is compatible with anisotropic earth models of azimuthal isotropy. The study area was divided in six regions with similar surface-wave phase velocities. We determined their corresponding SH and SV-velocity models versus depth (from 0 to 260 km) by means of the anisotropic inversion of surface-wave phase velocities under the hypothesis of surface-wave propagation in slightly anisotropic media. We observed seismic anisotropy from 10 to 100 km depth. From these models, the parameter ξ was calculated for each region, and the most conspicuous features of the study area were described in terms of this parameter, such as the existence of the plume material propagation in the Arabian shield from the Afar plume, or the existence of a lithospheric keel, which was observed in previous studies beneath the Arabian platform, the Mesopotamian Plain and the Zagros belt.