Seismicity of the eastern Mediterranean region: Perspective from the Sinai subplate

We conducted a comprehensive study of the seismicity of the eastern Mediterranean and examined its relation to the regional plate tectonics. Based on various published catalogs, we have constructed a new list of M_L ≥ 4 earthquakes which were recorded during the years 1900-1991 and represents most of the seismic moment released in the area over this period. b-values are 1.02, 1.0 and 1.07 for the whole Sinai subplate, the Dead Sea transform and the Cypriot arc, respectively. Seismic efficiency of the Dead Sea transform is very low (about 7%!), stressing the role of aseismic deformation in that plate border. Most of the major and moderate events, M_L ≥ 5, occur in belts associated with the geologically documented borders of the Sinai subplate: the Cypriot convergent arc in the north, the Dead Sea transform in the east and the rift of Suez in the southwest (the latter, like the Gulf of Eilat (Aqaba), was considered aseismic during the first half of the century). The northwestern border, however, could not be delineated. Low-level activity appears within the subplate, especially north of latitude 32°N, reflecting the breakdown of this part of Sinai as it approaches the Cypriot convergence zone. Though most of the seismic moments tend to concentrate along the subplate borders, some moderate activity spreads out in wide belts which reflect the complexity of deformation accompanying motion along the subplate borders.