The key role of conjugate fault system in importing earthquakes into the eastern flank of the Red Sea

Abstract

AbstractThis study aims to synthesize seismic observations with gravity and magnetic data and to suggest a new scenario on the development of the Harrat Lunayyir (HL) tectonic system on the eastern Red Sea coastline, Saudi Arabia. Gravity and aeromagnetic anomalies distinctly mapped the NE and NW trends, while the InSAR data depict a small NW–SE graben and an NW–SE dyke. High-resolution relocations, which are well-consistent with the focal mechanism solutions for events with magnitudes greater than 3.0, admit two distinctly fault styles of different orientations. Thus, leading to the NE and NW fault planes’ reactivation related to the Precambrian basement faults and the Red Sea rift system, respectively. The spatiotemporal distributions of epicenters and focal mechanism solutions suggest a new seismic deformation scenario of the 2009 earthquake seismic activity. The low static frictions of 0.2–0.35 obtained from the stress inversion indicates reactivation of preexisting faults in the respective seismogenic zones. The obtained results give rise to a swarm-like sequence of tectonic implications, two activated fault styles differently oriented, and an NE conjugate fault system inherited in the region, which plays a vital role in transferring the ambient stress regime into the Red Sea’s eastern flank.