ABSTRACT
To interpret geologic differences in the Red Sea and the origin of Cenozoic volcanism in western Arabia, we estimate high-resolution S-wave crustal and mantle velocity models using traveltime tomography and surface-wave tomography by incorporating data from dense seismic networks in the Arabian Peninsula. We also estimate radial anisotropy by simultaneously fitting Rayleigh and Love wave data. High crustal velocity, ultralow mantle velocity, and negative crustal anisotropy (VSH < V SV ) beneath the southern Red Sea indicate that hot material from the Afar mantle plume is feeding the formation of new oceanic crust through vertical dykes. We also found a north-extending low-velocity channel from Afar to Harrat Ithnayn and low-velocity anomalies in Harrat Ash Shamah at asthenospheric depths. Relatively weak positive anisotropy (~3%) is found beneath the two Harrats at lithospheric depths, with strong positive anisotropy (~6%–8%) in the nearby regions, which indicates the existence of two separate vertical dykes in the lithosphere, thereby confirming different source origins for the two Harrats from the asthenosphere.
