Seismicity of the Sinai subplate region: kinematic implications

The seismic activity of the Sinai subplate region on the basis of both hist orical (2200 B.C.-1900 A.D.) and recent (1900-1995) earthquake catalogs hav e been evaluated. Moderate and large earthquakes occurred mainly at the sub plate boundaries, Dead Sea Fault (DSF) system in the east, Cyprean are in t he north, and Suez rift in the southwest. Along the Dead Sea Fault system the activity concentrated at the southern a nd central segments. The earthquake distribution appears to have a tendency to cluster in time and space. The swarms (February, 1983; April, 1990; Aug ust, 1993 and November, 1995) in the Gulf of Aqaba indicate that the southe rn segment of the Dead Sea Fault system is the most seismogenic through the last two decades. North of the Dead Sea depression the seismic activity te nds to have occurred with NW trend to extend under the Levantine Sea. Altho ugh the northern segment of the Dead Sea Fault system is well defined from geological, geophysical and historical earthquake activity recent seismic a ctivity is practically absent especially north of Latitude 34 degrees N. In the eastern Mediterranean the seismicity is much higher in the area of t he Hellenic are than in the Cyprean are. Moreover, the activity occurs in a wide belt suggesting that the plate boundary is a deformation zone instead of a single line. The seismic activity in the Gulf of Suez is scattered and does not have any distinct trend. However, three active zones are delineated. At the mouth o f the gulf most of activity is concentrated where the Sinai triple junction (Africa, Arabia, Sinai) is situated. The central part and the northern par t of the gulf include the adjacent area as far as the river Nile. Actually, the activity is markedly decreased from south to north. Although there is no seismological evidence that the Suez rift continues in to the eastern Mediterranean, the activity in the Gulf of Suez region canno t be ignored. The parameters of magnitude-frequency relation (a, b) indicate that the lev el of earthquake activity in the Sinai subplate region is generally moderat e. Moreover, the energy release curve shows a regular trend and reflects oc casional high activity. (C) 1999 Elsevier Science Ltd. All rights reserved.