Coseismic displacements along the Serghaya fault:  An active branch of the Dead Sea fault system in Syria and Lebanon

Francisco Gomez  (Institute for the Study of the Continents, Cornell University, Ithaca, New York  14853)
Mustapha Meghraoui  (Institut de Physique du Globe, Strasbourg, France)
Abdul Nasser Darkal  (Department of Geology, Damascus University, Damascus, Syria)
Charles Tabet, Mohamad Khawlie (National Council for Scientific Research, Beirut, Lebanon)
Kamal Khair  (Department of Geology, American Univ. of Beirut, Lebanon)
Reda Sbeinati, Ryad Darawcheh  (Atomic Energy Commission, Damascus, Syria)
Muawia Barazangi  (Institute for the Study of the Continents, Cornell University, Ithaca, New York  14853)

The left-lateral Dead Sea fault system (DSFS) bends 30° through western Syria and eastern Lebanon and branches into the Serghaya and Yammouneh faults.  Active strike-slip faulting along the Serghaya fault is expressed as stream displacements, shutter ridges, and pull-apart basins, which are evident in satellite imagery (Landsat TM and SAR) and field observations.  Recent field studies along the Serghaya fault document the last coseismic displacement, including a free face still present along the fault scarp in several locations.  Carbon dating of charcoal and plant remains from the uppermost faulted deposit in two “trench” excavations along the fault consistently yields “modern” ages (i.e., since 1650 AD).   Displaced drainages and fault scarp profiles documenting the last faulting episode were measured in the Zebadani Valley.  Minimum sinistral offsets of 1.9 – 2.2 meters and vertical displacements of 0.4 – 0.7 meters are consistent with the 10 – 15 degree rakes of slickenside striations exposed in the fault zone, and these imply a total coseismic displacement of 2.0 – 2.3 meters.  Expressions of very recent faulting are observed over a minimum distance of 30 km along the fault from the southern Zebadani Valley (Syria) northeastward across the Lebanese border.  Assuming the displacements represent one earthquake, it seems that a large earthquake with M 6.8 – 7.2 involving about 50 – 60 km of total fault length probably occurred within the last 2 to 3 centuries.  It appears that the Serghaya fault may accommodate a significant part of the active deformation of the DSFS, and therefore, represents an important earthquake hazard for the metropolitan centers of Damascus and Beirut.