Abstract
SUMMARY 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.
Highlights
The Dead Sea fault system (DSFS) is the left-lateral transform boundary between the Arabian and Sinai plates as they converge with Eurasia
The Global Positioning System (GPS) velocities suggest possible ongoing shortening across the Palmyride fold belt. These results suggest that the kinematics of the northern DSFS deviate significantly from what is expected based on regional plate models that assume coherent Sinai and Arabia plates
In order to infer the slip rate for the northern DSFS, we examine profiles of the GPS velocities across the fault
Summary
The Dead Sea fault system (DSFS) is the left-lateral transform boundary between the Arabian and Sinai plates as they converge with Eurasia. In addition to the slip along the northern Dead Sea fault, there have been suggestions of active internal deformation within the northern Arabian Plate, most significantly along the Palmyride fold belt (Chaimov et al 1990). The northern Dead Sea fault demonstrates slower GPS velocities (and a slower slip rate) than are observed along the sections of the transform farther south. The GPS velocities suggest possible ongoing shortening across the Palmyride fold belt. Overall, these results suggest that the kinematics of the northern DSFS deviate significantly from what is expected based on regional plate models that assume coherent Sinai and Arabia plates. The results presented here will have significant implications for revising plate models, as well as the regional earthquake hazard
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