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ArRajehi A.,King Abdulaziz City for Science and Technology | McClusky S.,Massachusetts Institute of Technology | Reilinger R.,Massachusetts Institute of Technology | Daoud M.,Syrian National Earthquake Center | And 13 more authors.
Tectonics | Year: 2010

Five years of continuously recording GPS observations in the Kingdom of Saudi Arabia together with new continuous and survey-mode GPS observations broadly distributed across the Arabian Peninsula provide the basis for substantially improved estimates of present-day motion and internal deformation of the Arabian plate. We derive the following relative, geodetic Euler vectors (latitude (̊N), longitude (̊E), rate (̊/Myr, counterclockwise)) for Arabia-Nubia (31.7 ± 0.2, 24.6 ± 0.3, 0.37 ± 0.01), Arabia-Somalia (22.0 ± 0.5, 26.2 ± 0.5, 0.40 ± 0.01), Arabia-India (18.0 ± 3.8, 87.6 ± 3.3, 0.07 ± 0.01), Arabia-Sinai (35.7 ± 0.8, 17.1 ± 5.0, 0.15 ± 0.04), and Arabia-Eurasia (27.5 ± 0.1, 17.6 ± 0.3, 0.404 ± 0.004). We use these Euler vectors to estimate present-day stability of the Arabian plate, the rate and direction of extension across the Red Sea and Gulf of Aden, and slip rates along the southern Dead Sea fault south of the Lebanon restraining bend (4.5-4.7 ± 0.2 mm/yr, left lateral; 0.8-1.1 ± 0.3 mm/yr extension) and the Owens fracture zone (3.2-2.5 ± 0.5 mm/yr, right lateral, increasing from north to south; 1-2 mm/yr extension). On a broad scale, the Arabian plate has no resolvable internal deformation (weighted root mean square of residual motions for Arabia equals 0.6 mm/yr), although there is marginally significant evidence for N-S shortening in the Palmyride Mountains, Syria at ≤1.5 mm/yr.We show that present day Arabia plate motion with respect to Eurasia is consistent within uncertainties (i.e., ±10%) with plate tectonic estimates since the early Miocene when Arabia separated from Nubia. We estimate the time of Red Sea and Gulf of Aden rifting from present-day Arabia motion, plate tectonic evidence for a 70% increase in Arabia-Nubia relative motion at 13 Ma, and the width of the Red Sea and Gulf of Aden and find that rifting initiated roughly simultaneously (±2.2 Myr) along the strike of the Red Sea from the Gulf of Suez to the Afar Triple Junction, as well as along the West Gulf of Aden at 24 ± 2.2 Ma. Based on the present kinematics, we hypothesize that the negative buoyancy of the subducted ocean lithosphere beneath the Makran and the Zagros fold-thrust belt is the principle driver of Arabia-Eurasia convergence and that resisting forces associated with Arabia-Eurasia continental collision have had little impact on plate motion. © 2010 by the American Geophysical Union. Source

Mahmouda Y.,University of Strasbourg | Masson F.,University of Strasbourg | Meghraoui M.,University of Strasbourg | Cakir Z.,Technical University of Istanbul | And 6 more authors.
Journal of Geodynamics | Year: 2013

The Hatay Triple Junction (HTJ) is a tectonically complex area located at the intersection between the left-lateral East Anatolian fault (EAF), the Cyprus subduction arc and the left-lateral Dead Sea fault (DSF) which is a transform boundary between the Arabian and Sinai plates as they converge toward Eurasia. Previous GPS studies indicate a left-lateral strike-slip rate across the DSF varying from 5 mm/yr (along the southern part) to 2 mm/yr (along the northern part) (Alchalbi et al., 2010; Gomez et al., 2007; Le Béon et al., 2008; Mahmoud et al., 2005; Al-Tarazi et al., 2011). In contrast, the EAF has a roughly constant velocity along strike estimated at 9.7 + 0.9 mm/yr (Reilinger et al., 2006). The HTJ contains several well-identified active fault segments (DSF, EAF, Osmaniye fault, Karasu fault, Latakia fault, Jisr-al-shuggur fault, Idleb fault and Afrin fault) (Meghraoui et al., 2011), the fault-slip rates for which are poorly constrained. In order to constrain better the slip rate on faults, we established a network of 57 GPS sites in NW Syria and in SE Turkey. The first campaign was carried out in September 2009; a second took place in September and November 2010 and a third (only in Turkey) in September 2011. Although the velocity field vectors computed from the 2009, 2010 and 2011 measurements appear consistent with other local studies, the results are hampered by large uncertainties due to the short observation period. However, preliminary interpretations are consistent with decreasing velocity along the DSF from south to north reported previously. © 2012 Elsevier Ltd. Source

Alchalbi A.,Syrian National Earthquake Center | Daoud M.,Syrian National Earthquake Center | Gomez F.,University of Missouri | McClusky S.,Massachusetts Institute of Technology | And 12 more authors.
Geophysical Journal International | Year: 2010

New Global Positioning System (GPS) measurements in NW Syria provide the first direct observations of near-field deformation associated with the northern Dead Sea fault system (DSFS) and demonstrate that the kinematics of the northern section of this transform plate boundary between the Arabian and Sinai plates deviate significantly from plate model predictions. Velocity estimates based on GPS survey campaigns in 2000, 2007 and 2008, demonstrate left-lateral shear along the northern DSFS with 1σ uncertainties less than 0.7 mm yr-1. These velocities are consistent with an elastic dislocation model with a slip rate of 1.8-3.3 mm yr-1 and a locking depth of 5-16 km. This geodetically determined slip rate is about half of that reported farther south along the central section (Lebanese restraining bend) and the southern section (Jordan Valley and Wadi Araba) of the transform and consequently requires some deformation to occur away from the transform along other geological structures. The factor of two difference in slip rates along the transform is also consistent with differing estimates of total fault slip that have occurred since the mid Miocene: 20-25 km along the northern DSFS (in NW Syria) versus about 45 km along the southern DSFS segment. Some of the strain deficit may be accommodated by north-south shortening within the southwestern segment of the Palmyride fold belt of central Syria. Additionally, a distinct change in velocity occurs within the Sinai plate itself. These new GPS measurements, when viewed alongside the palaeoseismic record and the modest level of present-day seismicity, suggest that the reported estimates of recurrence time of large earthquakes (M > 7) along the northern section of the DSFS may be underestimated owing to temporal clustering of such large historical earthquakes. Hence, a revised estimate of the earthquake hazard may be needed for NW Syria. © 2009 The Authors Journal compilation © 2009 RAS. Source

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