Slip distribution model of two small-sized inland earthquakes and its tectonic implication in north-eastern desert of Egypt

Two slip distribution models of the 1999 and 2006 Beni-Suef earthquakes (M(w) 4.5 and M(w) 4.2, respectively) were revealed using waveform inversion with an empirical Green's function method. Waveform data used were recorded by the Egyptian Seismic Network's short-period stations. To identify the active fault plane associated with each event and to estimate the best fitting rupture velocity, a set of slip distribution models was recovered on both nodal planes of the focal mechanism with a range of fixed rupture velocities. The result for the 1999 event shows that the northwest trending plane consistently provided better fitting solutions than the southwest trending plane. This implies that the slip was left-lateral on a northwest trending plane dipping toward the southwest. The 2006 event caused a slip movement on a dip-slip fault dipping towards the north. The rupture velocities were founded to be 3.5 km/s and 3.0 km/s which gave a comparatively small residual for the 1999 and 2006 earthquakes, respectively. The corresponding slip distribution models for the 1999 and 2006 events provide their seismic moments of 7.6E + 15 N m and 2.5E + 15 N m and moment magnitudes of 4.5 and 4.2, respectively. From the viewpoint of tectonics in the region, the present results imply an extensional tectonic process along the pre-existing WNW-ESE/NW-SE faults that may be transferred from the Gulf of Suez-Red Sea rift towards the northeastern desert in Egypt. This finding implies the diving of the northeastern of African plate beneath the Eurasian plate. (C) 2011 Elsevier Ltd. All rights reserved.