First indications of high slip rates on active reverse faults NW of Damascus, Syria, from observations of deformed Quaternary sediments: Implications for the partitioning of crustal deformation in the Middle Eastern region

Abstract

Recent research on rates of crustal shortening within the Palmyra Fold Belt (PFB) in Syria has drawn attention to the possibility that reverse faults near the city of Damascus, which adjoins the SW PFB, have significant slip rates. We infer that the Damascus Fault, directly adjacent to the city, has developed a throw of ~2500m and report the discovery of the en echelon Bassimeh Fault, with a throw of ~1000m, this fault being revealed by warping of the local bedrock and of a terrace, of inferred Late Pleistocene age, of the River Barada. We estimate that this set of faults became active circa 0.9Ma, synchronous with changes to the pattern of faulting previously reported farther southwest in the northern Jordan Valley. Vertical slip rates on the Bassimeh and Damascus faults of ~1.1 and ~2.8mm a−1, respectively, are thus estimated. We also infer that large historical earthquakes, previously attributed to left-lateral faulting farther west on the Dead Sea Fault Zone (DSFZ), probably occurred on this set of reverse faults; these faults thus represent a significant hazard to the city of Damascus. Our observations indicate that as much as half of the northward motion of the Arabian plate, relative to the African plate, may be ‘absorbed’ by crustal shortening within the PFB, potentially explaining the low slip rate recently measured geodetically on the northern DSFZ in western Syria.