Title : Moho undulations and high Poisson’s ratio beneath volcanic areas, west of Saudi Arabia: indication of asymmetric lithospheric uplift
Abstract:
By utilizing teleseismic data, the P-wave receiver functions (RFs) have been computed for 20 broadband seismic station deployed in Harrat Khaybar and Ithnayn, in the Arabian Shield area, western of Saudi Arabia. The RFs are modeled to investigate the crustal structure, represented by determining of crustal thickness, mean crustal Vp/Vs ratio, and the Poisson’s ratio. No previous studies have provided information on crustal structure using seismological data for several parts of Harrat Khyber, and therefore this study provides new information about the crustal structure for those parts. Results revealed that the crustal thicknesses range from 30 to 37 km, verifying an indication of undulated Moho interface and asymmetric mantle uplift beneath the study area.
The asymmetry could relate to a simple shear extension under the study area, or due to the pre-existing lateral variations of crustal thickness. The observed Vp/Vs values that range from 1.71 to 1.82 seem to have a direct relationship with the crustal thickness (i.e., crust of smaller depth corresponds to high Vp/Vs). The high Poisson’s ratios throughout some areas beneath Khayber and Ithnayn area (~ 0.30) indicate that the crust is more mafic in composition than a typical continental crust, probably referring to intrusion of mafic dikes into the lower crust. In contrast to previous studies, results of this study revealed that some areas of Harrat Khaybar and Ithnayn have high Vp/Vs ratios with respect to the rest of the Arabian shield; however, it is consistent with the results of other previous studies.
