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

Although the precise boundaries and kinematics of the Sinai subplate are still doubtful, it has a significant role in the tectonic evolution of the northern Red Sea region. On the basis of earthquake distribution, the Sinai region can be considered as a subplate partially separated from the African plate by the Suez rift. The relative motion between Africa, Sinai and Arabia 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 107 km since the Middle Miocene, in contrast to the northern segment where only 25 to 35 km offset can be inferred. We think that along the southern segment the total displacement was 72 km until the late Miocene (10 Ma). The earthquake activity is strongly reduced along the northern segment of the Dead Sea fault system. Therefore, we suggest that the northern part (Yammouneh 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 northern 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 is 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 the northern Red Sea. We suggest that the Dead Sea strike-slip fault was active since Middle Miocene time (15 Ma) with a slip rate of 0.72 cm/a to provide a total displacement of about 107 km. This strike-slip motion occurred about an Euler pole near 33.0 degrees N, 21.0 degrees E with a rotation angle of 3.0 degrees. It can be inferred from the proximity of the pole and angle of rotations for the Red Sea and Dead Sea fault that more than 85% of the 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 320 km west of the Nile Delta. The rate of motion through the last 15 Ma (Middle Miocene) is about 0.1 cm/a and the angle of rotation is 0.9 degrees. During this period the total opening of the Suez rift is 15 km, while the rest of the motion (45 km) occurred mainly through the first phase of the development before the Middle Miocene. (C) 1999 Elsevier Science Ltd. All rights reserved.