Surface wave velocities across Arabia

The group-velocity distribution beneath the Arabian Plate is investigated u sing Love and Rayleigh waves. We obtained a balanced path coverage using se ismograms generated by earthquakes located along the plate boundaries. We m easured Love- and Rayleigh-wave group-velocity dispersion using multiple fi lter analysis and then performed a tomographic inversion using these observ ations to estimate lateral group velocity variations in the period range of 5-60 s. The Love- and Rayleigh-wave results are consistent and show that t he average group velocity across Arabia increases with increasing period. T he tomographic results also delineate first-order regional structure hetero geneity as well as the sharp transition between the Arabian shield and the Arabian platform. Systematic differences are observed in the distribution o f the short-period group velocities across the two provinces, which are con sistent with surface geology. The slower velocities in the platform reveal the imprint of its thick sedimentary section, while faster velocities corre late well with the exposed volcanic flows in the shield. Shear-wave velocit y models for the two regions, obtained from the inversion of the group velo cities, confirm results from previous studies of higher S-wave velocity in the upper crust beneath the shield. This may be due to the present remnants of the oceanic crust (ophiolite belts) associated with the island arcs evo lutionary model of the Arabian shield. The mapping of the surface-wave group velocity using a large data can be us ed in constraining the regional structure at existing and planned broadband stations deployed in this tectonically complex region as part of the seism ic monitoring under CTBT.