Abstract
This 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.
Highlights
The current geodynamic process acting in the Red Sea is characterized by the extensional tectonic stress regime as accommodated by the Arabian plate’s divergence movement away from the African plate (Stoeser and Camp 1985; Abdelfattah et al 2020)
This study focused on the Harrat Lunayyir (HL) seismogenic and volcanic zone in the western shield of Saudi Arabia, which has a complex structure comprises dykes, recent volcanic eruptions, and fault segments of various orientations
We performed an integrated analysis based on gravity and seismological data, considering the results obtained from previous studies, such as magnetic anomalies, the model of InSAR data, and earthquake spectral characteristics
Summary
The current geodynamic process acting in the Red Sea is characterized by the extensional tectonic stress regime as accommodated by the Arabian plate’s divergence movement away from the African plate (Stoeser and Camp 1985; Abdelfattah et al 2020). Abdelfattah et al Earth, Planets and Space (2021) 73:178 One of these regions is the Harrat Lunayyir (HL) enriched by the active volcanic field. The HL is a part of the Arabian Shield that comprises the Red Sea’s eastern flank. It attracts global interest because of the 2009 earthquake episode of the largest event with magnitude Mw 5.4, preceded by thousands of events. Since this seismic event, scientists debate whether the HL’s earthquakes were due to tectonic or magma upwelling through the crust.
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