Source characterization and ground motion modeling computed from the 3 September 2015 earthquake, Western Desert, Egypt

Abstract

To obtain the characterized source model for prediction of strong ground motions, the ground motion generation area and rupture geometry of an inland crustal earthquake from near-source ground motion records has been estimated. An earthquake, with a magnitude of 4.3 ML and a focal depth of 18 km occurred on September 3, 2015 at 30.45N, 28.44E in the Western Desert of Egypt about 60 km south of El-Dabaa city. This earthquake is the first instrumentally recorded earthquake occurring in this area in several decades. The waveform data of this event has been used for source characterization and ground motion modeling. The present work describes the results of a preliminary study conducted to obtain fault plane solutions of this earthquake from waveform inversion and P-wave polarity. For this purpose, the source parameters related to the strong ground motion were estimated by waveform data and first arrivals recorded by the Egyptian National Seismic Network (ENSN) are used to arrive at focal mechanism solutions. Fault plane solutions for the main shock indicate strike-slip motion. One nodal plate strikes about 330°, is nearly vertical, and indicates right lateral slip. The other nodal plane strikes about 240°, dips very steeply NW, and indicates left lateral slip. Also the peak ground acceleration (PGA) at the El-Dabaa site has been simulated by taking into account an accurate estimation of the source characterization, the path attenuation model, and site amplification. The results have been validated using an actual recording of PGA at one ENSN station that recorded strong ground motion.