Geophysical evidences on reactivation of NE faults in southern Arabian Shield and its tectonic implications

Abstract

The Eastern flank of the Red sea represents an uplifted Precambrian basement that is known as the Arabian Shield. Different tectonic events were activated since the collisions among continental fragments that occurred during the period 630–550 Ma, showing very old NE ophiolite-suture zones, North trend shear zones, belts, folds, and NW Sinistral fault system known as Najd shear zones. Thus, heterogeneities and inherited faults are expected in the old basement; however, based on surface observations, NE trend faults are not described in the Arabian Shield. Despite the inconsistency with the background tectonic model of the Red Sea rifting, recent seismological studies show that active NE faults may exist in western Arabian Shield. This study aims to investigate and map the fault system in southern Arabian Shield and then better understand the tectonic system acting in the region. We provide an analysis that incorporates gravity, magnetic, and seismological data in Namas area, where earthquake sequence occurred in 2017. Using the regional-residual separation, filtering and edge detector function techniques, we identified NE trend inherited faults within the Precambrian basement that might be seismically active, as shown by the obtained distribution of epicenters and focal mechanism solutions of strike-slip style among the 2017 Namas Earthquake sequence. This result emphasizes the preexistence of a potential local tectonic process that is incongruous with the regional stress regime.