Analysis of the southeast Beni-Suef, northern Egypt earthquake sequence

Oil I I October 1999, a moderate earthquake of local magnitude NIL 4.9 hit northern Egypt. This event shook, the greater Cairo region and northern part of the Nile valley and vas felt in Much of northern Egypt,,with epicentral intensity of V (EMS). It was followed by eight aftershocks,with local magnitude ranging from 1.6 to 3.2. A detailed analysis of this sequence, cross-correlation analysis, fault plane Solutions and source parameter estimations is performed in the present article. A cross-correlation analysis allowed Lis to recognize a number of correlated events,,which were used for earthquake ancestry using a master event technique. The focal mechanism solutions for the main-shock and the largest aftershock are moderately controlled and indicate strike-slip faulting with a dip-slip normal component. Rupture directivity. aftershock distributions and isoseismal lines were combined in an attempt to determine which of the two nodal planes is the fault plane. The dynamic source parameters of the southeast Beni-Suef earthquake sequence hake been estimated from the P-wave spectra of the Egyptian National Seismograph Network (ENSN). The spectral amplitude of the main shock records displayed two distinct corner frequencies that reflect a complex rupture process. The averaging of the obtained values at different stations shows that the main shock occurred on a fault length of 1.5 km with relative displacement 9 cm, stress drop of 49 bar and seismic moment of 5 x 10(22) dyn/cm. The aftershocks show a relatively similar source parameters fault length of 0.3less than or equal toLless than or equal to0.6 km, relative displacement of 0.05less than or equal to(u) over bar less than or equal to0.2 cm, seismic moment of 2.3x10(19)less than or equal toM(0)less than or equal to1.1x10(20) dyn.cm and stress drop of 0.7less than or equal toDeltasigmaless than or equal to4 bar. (C) 2002 Elsevier Science Ltd. All rights reserved.