The Sinai subplate and tectonic evolution of the northern Red Sea region

Although the precise boundaries and kinematics of the Sinai subplate are st ill doubtful, it has a significant role in the tectonic evolution of the no rthern Red Sea region. On the basis of earthquake distribution, the Sinai r egion can be considered as a subplate partially separated from the African plate by the Suez rift. The relative motion between Africa, Sinai and Arabi a is the main source generating the present-day earthquake activity in the Gulf of Suez and the Gulf of Aqaba regions. According to geological observations, the southern segment of the Dead Sea fault system can be characterized by a left-lateral displacement of about 1 07 km since the Middle Miocene, in contrast to the northern segment where o nly 25 to 35 km offset can be inferred. We think that along the southern se gment the total displacement was 72 km until the late Miocene (10 Ma). The earthquake activity is strongly reduced along the northern segment of the D ead Sea fault system. Therefore, we suggest that the northern part (Yammoun eh fault) evolves through initial cracking of the crust due to build-up of stress since the Pliocene time (5 Ma) and propagates northward into Lebanon and Syria. This last 5 million years is the period when the southern and n orthern segments became linked and formed a single fault system with a new displacement of 35 km. According to the proposed model the predicted opening pole of the Red Sea i s near 34.0 degrees N, 22.0 degrees E with an angle of total rotation of 3. 4 degrees since the early Miocene, providing a 0.82 cm/a opening rate in th e northern Red Sea. We suggest that the Dead Sea strike-slip fault was acti ve since Middle Miocene time (15 Ma) with a slip rate of 0.72 cm/a to provi de a total displacement of about 107 km. This strike-slip motion occurred a bout an Euler pole near 33.0 degrees N, 21.0 degrees E with a rotation angl e of 3.0 degrees. It can be inferred from the proximity of the pole and ang le of rotations for the Red Sea and Dead Sea fault that more than 85% of th e motion has been accommodated on the Gulf of Aqaba and the Dead Sea fault and less than 15% in the Gulf of Suez. This model predicts a normal extensional motion in the Gulf of Suez with a minor left-lateral strike-slip component. We expect the pole of this motion to be at 31.0 degrees N, 29.0 degrees E, offshore of Alamein city about 32 0 km west of the Nile Delta. The rate of motion through the last 15 Ma (Mid dle Miocene) is about 0.1 cm/a and the angle of rotation is 0.9 degrees. Du ring this period the total opening of the Suez rift is 15 km, while the res t of the motion (45 km) occurred mainly through the first phase of the deve lopment before the Middle Miocene. (C) 1999 Elsevier Science Ltd. All right s reserved.