Lithospheric structure of the Arabian Shield from joint inversion of P- and S-wave receiver functions and dispersion velocities

Abstract

New velocity models of lithospheric thickness and velocity structure have been developed for the Arabian Shield by three tasks: 1) Computing P-Wave Receiver Functions (PRFs) and S-Wave Receiver Functions (SRFs) for all the broadband stations within the Saudi seismic networks. The number of receiver function waveforms depends on the recording time window and quality of the broadband station. 2) Computing ambient noise correlation Green’s functions for all available station pairs within the Saudi seismic networks to image the shear velocity in the crust and uppermost mantle beneath the Arabian Peninsula. Together they provided hundreds of additional, unique paths exclusively sampling the region of interest. Both phase and group velocities for all the resulting empirical Green’s functions have been measured and to be used in the joint inversion. 3) Jointly inverted the PRFs and SRFs obtained in task 1 with dispersion velocities measured on the Green’s functions obtained in task 2 and with fundamental-mode, Rayleigh-wave, group and phase velocities borrowed from the tomographic studies to precisely determine 1D crustal velocity structure and upper mantle. The analysis of the PRFs revealed values of 25-45 km for crustal thickness, with the thin crust next to the Red Sea and Gulf of Aqaba and the thicker crust under the platform, and Vp/Vs ratios in the 1.70-1.80 range, suggesting a range of compositions (felsic to mafic) for the shield’s crust. The migrated SRFs suggest lithospheric thicknesses in the 80-100 km range for portions of the shield close to the Red Sea and Gulf of Aqaba and near the Arabian Gulf. Generally, the novelty of the velocity models developed under this paper has consisted in the addition of SRF data to extend the velocity models down to lithospheric and sub-lithospheric depths.

Asthenospheric Flow of Plume Material Beneath Arabia Inferred From S Wave Traveltime Tomography

“…Journal of Geophysical Research: Solid Earth et al, 2006). The depth extent of the lithosphere beneath the Arabian platform is estimated to be shallower than 200 km by previous receiver function studies (Al-Amri, 2015;Hansen et al, 2007;Tkalčić et al, 2006) and 200-250 km by a body-wave tomography study (Koulakov et al, 2016). Therefore, high-velocity anomalies deeper than 300 km beneath the Arabian platform are likely caused by strong vertical smearing due to poor resolution for the region (Figures 5 and 6).…”

“…This velocity difference may reflect a contrast between hot mantle upwelling from the asthenosphere beneath the Arabian shield responsible for harrat formation and cold, thick lithosphere beneath the Arabian platform (Al‐Amri, 2015; Hansen et al, 2007; Tkalčić et al, 2006). The depth extent of the lithosphere beneath the Arabian platform is estimated to be shallower than 200 km by previous receiver function studies (Al‐Amri, 2015; Hansen et al, 2007; Tkalčić et al, 2006) and 200–250 km by a body‐wave tomography study (Koulakov et al, 2016). Therefore, high‐velocity anomalies deeper than 300 km beneath the Arabian platform are likely caused by strong vertical smearing due to poor resolution for the region (Figures 5 and 6).…”

“…In Section A‐a across Harrat Lunayyir, Harrat Ithnayn, and Harrat Hutaymah, a sharp velocity contrast between the Arabian shield and the Arabian platform is observed. This velocity difference may reflect a contrast between hot mantle upwelling from the asthenosphere beneath the Arabian shield responsible for harrat formation and cold, thick lithosphere beneath the Arabian platform (Al‐Amri, 2015; Hansen et al, 2007; Tkalčić et al, 2006). The depth extent of the lithosphere beneath the Arabian platform is estimated to be shallower than 200 km by previous receiver function studies (Al‐Amri, 2015; Hansen et al, 2007; Tkalčić et al, 2006) and 200–250 km by a body‐wave tomography study (Koulakov et al, 2016).…”