Seismological Aspects of the Abou Dabbab Region, Eastern Desert, Egypt

Abstract

Located about 24 km from the Red Sea, the Abou Dabbab region is characterized by significant microseismic activity. The seismic history of this region is marked by two moderate magnitude earthquakes, the 12 November 1955 Mb 6.1 and the 2 June 1984 Mb 5.1. The 1955 Mb 6.1 earthquake was the largest recorded event to occur within Abou Dabbab. Woodward Clyde Consultants (1982) computed the first-motion focal mechanism for the 1955 event. The mechanism has a strike-slip faulting solution with a normal dip-slip component. The T -axis has a NNW trend. The two nodal planes that were determined for this event give NNW to NW and ENE to ESE strike directions. Earthquakes in the Abou Dabbab region have shown a tendency to cluster in space and time (Morgan et al. 1981). This pattern suggests that the activity seems to have been mainly controlled by local sources ( e.g. , magmatic intrusion) triggered in turn by regional tectonics (Badawy et al. 2008). The heat flow value in Abou Dabbab is twice the average heat flow value in the Eastern Desert of Egypt (Morgan et al. 1985). El Hady (1993) reported from the distribution of earthquake's focal depths and rheological studies that the brittle-ductile transition in the Abou Dabbab area occurs at a relatively shallow depth range (∼9–1. km). The existence of the brittle-ductile transition in this region can be attributed to shallow asthenospheric intrusion, which causes an increase in the temperature. Recordings of microearthquakes in Abou Dabbab from 1 August to 20 August 2004 from 11 portable instruments show that this region is distinguished by intense spatial clustering (Figure 1A). The error estimated in both horizontal distance and depth is less than 0.3 km (Hussein et al. 2008). The cross-section perpendicular to the activity reflects two main spatial clusters with a …