Crustal Structure Beneath the Arabian Shield Based on the Receiver Function Method

Abstract

Arabian Shield occupying the western part of the Arabian Peninsula is an area where strong heterogeneities in crustal structures are associated with several factors, such as an ongoing rifting process in the Red Sea basin, massive recent effusive volcanism in several large basaltic fields (harrats), as well as traces of complex tectonic evolution of this area in Precambrian due to the accretion of several terrains. Geophysical studies of the crust give important information to identify the roles of these and other factors. Receiver function is one of the most robust and relatively inexpensive tools to derive the depths of the major interfaces, of which Moho is the most important, as well as mean velocity parameters in the crust. Based on the H-k stacking method, we have determined the Moho depths and the mean Vp/Vs ratios below a number of seismic stations distributed on the Arabian Shield. As in most of previous studies, we have identified a gradual increase of the crustal thickness from 25 km in the coastal areas of the Red Sea to ~40 km in the eastern margin of the shield. The crustal thickness distribution appears to be consistent with seismic velocity anomalies derived at 30 km depth in the tomography model by (El Khrepy, 2021). For the Vp/Vs ratio, we observe strong variations over the entire study area, and in some cases even between stations located close to each other. This is especially clear in areas of recent magmatism, such as in Harrats Lunayyir and Rahat, where stations with high Vp/Vs ratios correspond to zones with fresh monogenic cones and historical magmatic activity.