Seismicity and focal mechanisms of earthquakes in Egypt from 2004 to 2011

The focal mechanisms for 36 earthquakes in and around Egypt are constructed for the same period using the waveform data recorded by the Egyptian National Seismological Network (ENSN) and the International Data Center (IDC) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO). These solutions are computed by joining P, SH, SV polarities and SV/P, SH/P and SV/SH amplitude ratios where the quality of each solution is evaluated. This set of solutions is considered as a completion of the Egyptian focal mechanism catalogue. It will be helpful in understanding the spatial variation in the stress field within Egypt. At northern Egypt, the dominated mechanisms reflect a normal dip-slip, sometimes with strike component except in Dahshour region where strike-slip mechanism dominates. Toward the south, in Aswan source region, the strike-slip mechanism is dominated reflecting that the local tectonics is important characterized by a major strike slip component. The orientations of the T axes appear to be changed from NE-SW in the Gulf of Suez to ENE-WSW in the Gulf of Aqaba and NNE-SSW in the remains of the Egyptian territory. It is clear that Egypt is mainly controlled by extensional stress field.