Shear-wave splitting across western Saudi Arabia: The pattern of upper mantle anisotropy at a Proterozoic shield

We constrain upper mantle anisotropy across the Arabian Shield from shear-w ave splitting analyses of SKS phases at eight temporary broadband stations that operated in Saudi Arabia. The direction of fast polarization is consis tently aligned north-south and the delay time between fast and slow shear w aves is generally 1.0 to 1.5 s, indicating that the mantle anisotropy is re latively homogeneous and coherent. We cannot distinguish between two possib le models for the origin of this signal. The observed splitting may reflect fossil upper mantle anisotropy associated with the dominantly east-west ac cretion of oceanic terranes and formation of the Proterozoic Arabian lithos phere. Our results may also be compatible with present-day asthenospheric a nisotropy caused by the northward absolute plate motion of the Arabian plat e or northward asthenospheric flow from an Ethiopian mantle plume.