Multi-scale Inference of Lithospheric Seismic Structure in Saudi Arabia

Abstract

The complex geology of the Arabian plate together with the sparse nature of previous datasets have prevented a detailed characterization of the lithospheric structure and its spatial relationship to surface geology. With newly acquired large amount of seismic data, we investigate the crustal and upper-mantle velocity structure and develop highresolution 3-D shear-wave velocity models for Saudi Arabia using receiver functions and surface wave dispersion velocities. Our datasets, including teleseismic data for obtaining receiver functions and regional earthquake data for measuring Rayleigh-wave dispersion curves, are recorded by Saudi National Seismic Network (SNSN) stations operated by the Saudi Geological Survey (SGS). Our results reveal significant lateral variations in shearwave speeds of the crust and upper mantle, bulk Vp/Vs ratio, crustal thickness, and Lithosphere-Asthenosphere Boundary (LAB) depth beneath Saudi Arabia. Particularly, we notice interesting mantle-lid velocity and temperature patterns in which slow shearvelocities and high temperatures are observed below the southern and northern tips of the Arabian shield, compared with the values obtained for the central shield. Also, we detect high crustal bulk Vp/Vs ratios in Harrat Lunayyir and a few crustal low shear-velocity anomalies below the Cenozoic lava fields in the Arabian shield. In addition, a rather thin lithosphere and an upper-mantle low shear-velocity zone below western Arabia are imaged. We discuss our results and how they are related to previous geochemical observations, the origin of the Cenozoic volcanism, the influence of the Red Sea rift and the Afar plume on the volcanism, as well as possible plumbing system of magmas underneath western Arabia.