Reinvestigation of the 1978 Gilf El Kebir earthquake, Egypt

Abstract

ABSTRACT Four significant earthquakes located in the southern portion of the Western Desert were investigated to better understand the area tectonics. The retrieved solution of 9 December 1978, indicates a pure strike solution by using FOCMEC software, which our solution differs from the solution established in an earlier study. The focal mechanism solutions of the four events in the southern part of the Western Desert demonstrate a strike-slip faulting regime along E-W oriented faults, in contrast to the solutions for earthquakes in Northern Egypt, which exhibited normal faulting mechanisms with small strike-slip components. Forces exerted as a result of differences in the divergent spreading rates along the Red Sea plate boundary North and South of the zone between 22° and 24° N may lead to second-order stress fields. This, in turn causes an E-W shear couple that is directed towards the southern part of the Western Desert and rejuvenation of the E-W trending faults. The 1984 Abu Dabbab earthquake, which occurred near the Red Sea coast South of 24° N, provides support to this argument and exhibited a mechanism similar to the four events that took place in the southern part of the Western Desert.