The Gulf of Suez earthquake, 30 January 2012, northeast of Egypt

Abstract

The present day tectonic deformation within Egypt is related to the regional tectonic forces of the surrounding plate boundaries including the African–Eurasian plate margin, the Red Sea plate margin and the Levant transform fault in addition to the local tectonics of Egypt. Based on the spatial distribution of earthquake epicenters in Egypt, the most seismically active areas are located in the Northern Red Sea, Gulf of Suez, Gulf of Aqaba and Mediterranean coastal zone. On 30 January 2012, a moderate earthquake of local magnitude ML 4.6 struck the northeast part of Egypt, at the entrance of Gulf of Suez. This event was felt in many areas surrounding the epicenter with low damage recorded. To understand the mechanism and the reflected irregularity of the evolved stress field concerning the Gulf of Suez area, calculation of source parameters and source mechanisms of this event are necessary. Moment tensor inversion is used to retrieve the fault plain solutions and the seismic moment by using waveforms recorded by the Egyptian National Seismic Network. The fit between observed and synthetic seismograms was computed for an elastic layered media and minimized using a least squares algorithm. The derived source mechanism indicates normal faulting along NNW–SSE trending faults, in agreement with the rifting of the northern Red Sea in its northern branches (Gulf of Suez and Gulf of Aqaba). The source parameters are estimated and the derived corner frequency f o for the P-wave spectra shows a value of 3.00 Hz. The seismic moment M o is 1.278 × 1023 Nm, the fault length r is 0.8 km, the average displacement D 0 is 0.023 m, and the value of the stress drop Δσ is 1.10 MPa. The source mechanism and source parameters imply the continuous activity of the Red Sea rift system at the Gulf of Suez opening.