We conducted a comprehensive study of the seismicity of the eastern Me
diterranean and examined its relation to the regional plate tectonics.
Based on various published catalogs, we have constructed a new list o
f M(L) greater than or equal to 4 earthquakes which were recorded duri
ng the years 1900-1991 and represents most of the seismic moment relea
sed 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 are,
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) greater than or e
qual to 5, occur in belts associated with the geologically documented
borders of the Sinai subplate: the Cypriot convergent are in the north
, the Dead Sea transform in the east and the rift of Suez in the south
west (the latter, like the Gulf of Eilat (Aqaba), was considered aseis
mic during the first half of the century). The northwestern border, ho
wever, could not be delineated. Low-level activity appears within the
subplate, especially north of latitude 32 degrees N, reflecting the br
eakdown of this part of Sinai as it approaches the Cypriot convergence
zone. Though most of the seismic moments tend to concentrate along th
e subplate borders, some moderate activity spreads out in wide belts w
hich reflect the complexity of deformation accompanying motion along t
he subplate borders.