Seismicity and Seismotectonic Setting of the Red Sea and Adjacent Areas

Abstract

It was thought that the Kingdom of Saudi Arabia was characterized by low seismic activity and that the Arabian shield was relatively stable. After establishing the Saudi National Seismic Network and occurrence of some felt earthquakes in the Arabian Shield, this assumption changed, especially for the western part of the shield. A study of the most recent felt earthquakes in the Red Sea coastal plain area that were recorded by the Saudi National Seismic Network can help in better understanding the Red Sea rifting. Moment tensor inversion of the waveform data offers a unique insight into the active tectonics of the region as well as providing information for seismic hazard analyses of the western part of Saudi Arabia and the Gulf of Aqaba. Moment tensor analyses of recent earthquakes in the Red Sea coastal plain show that some Cenozoic faults are seismically active, with normal faulting under NE–SW tension and NW–SE compression. This is seen in the northern Red Sea, Gulf of Aqaba, and the Badr and Harrat Lunayyir earthquakes, whereas published moment tensor solutions of the largest earthquakes in and around the Arabian plate indicate that most of the earthquakes in eastern Saudi Arabia reflect reverse faulting with NE forces due to collision with the Eurasian plate. There is also an E–W tension axis acting on the Makkah–Madinah–Nafud volcanic line, in agreement with the fault plane solution of the Qunfudah earthquake. It is recommended that two seismically active regions on either side of the Red Sea (Abu Dabbab and Harrat Lunayyir) should be studied further, including their relation to the rifting of the Red Sea. The Saudi National Seismic Network plays an important role in a better understanding of the seismicity and seismotectonic setting of Saudi Arabia in particular and the Arabian plate in general, including providing data for hazard evaluations.