Seismicity and active tectonics of the Egyptian Red Sea margin and the northern Red Sea

Abstract

An active median spreading center has been identified in the Red Sea south of 22°N, but from published reports, the northern Red Sea appears to be essentially aseismic. We have used microearthquake monitoring techniques along the Egyptian Red Sea margin to investigate the active tectonics in the region and have found that the northern Red Sea is not aseismic. Events recorded with epicenters in the Red Sea define an active zone extending south-southeast from the Gulf of Suez into the axial region of the Red Sea down to 25.75°N, with additional microseismicity between 24° and 25°N, suggesting active median spreading in the northern Red Sea. Two areas of intense microearthquake activity have also been identified; the first at the southern end of the Gulf of Suez and the second in the Egyptian Red Sea Hills, clustered at approximately 25.28°N, 34.52°E. The Gulf of Suez seismicity results from the adjustments in motion at the triple junction between the African and Arabian plates and the Sinai subplate. The source of the seismicity in the Egyptian Red Sea Hills is unknown, but a uniform fault plane mechanism is not indicated by first motion studies or the spatial distribution of the hypocenters.