Source process of the October 12, 1992 Cairo earthquake

Abstract

Broadband body waves recorded at 12 digital seismic stations worldwide were used to study the source process of the October 12, 1992 Cairo earthquake. To study the source process of this event the P and SH waveforms from IRIS data center were inverted to double couple source using the method Kikuchi and Kanamori (1991) in which the rupture is presented by discrete subevents with various mechanisms. The best solution consists of only one event with a mechanism 270°/47°/-123° (strike/dip/slip), a normal faulting mechanism with small strike slip component. This solution is almost compatible with the previously suggested mechanisms for the same event. This event took place at a depth of 22 km. This depth explains the lack of surface faulting. The seismic moment is 7.2 ´ 10 17 Nm (Mw = 5.8) with a source duration of 4 s. The estimated fault length is about 11 km, the derived average dislocation (D) is 0.24 m, the stress drop (Ds ) is 1.85 MPa and the Orwan stress drop is 0.425 MPa.