Anelastic Tomography of the Arabian Plate

Abstract

ABSTRACT In this study, we investigate the upper-mantle structure of the Arabian plate based on anelastic full-waveform inversion. The Arabian plate is composed of two main geological provinces—the Arabian Platform in the east and the Arabian Shield in the west. The Shield is dotted with areas of Cenozoic volcanism (harrats) whose precise tectonic and geodynamic origin is still debated. To help shed light on the deep geophysical properties of the Arabia plate and seismic signatures in the Earth’s upper mantle related to the surface volcanism, we use ∼38,400 three-component waveforms filtered between 25 and 100 s from 64 well-distributed regional earthquakes. We fit frequency-dependent travel-time and amplitude information. We follow a hierarchical inversion strategy in which we initially invert for the elastic structure and subsequently for both the elastic and anelastic parameters simultaneously. We assess the resolution and trade-offs between model parameters by conducting point spread function tests. Our model reveals low-wavespeed anomalies associated with mantle material that may originate from the Afar plume. In addition, we identify significant shear attenuation anomalies in the southern and central regions of the western margin of the Arabian plate. We suggest that these anomalies are linked to either the hot asthenosphere from the Afar plume or partial melting triggered by lithospheric thinning along the Red Sea rift.