EARTHQUAKE SEQUENCES AND REGIONAL STRAIN PARTITIONING ALONG THE NORTHERN DEAD SEA FAULT (SYRIA AND LEBANON)

Recent paleoseismic and neotectonic studies along the northern Dead Sea fault system (DSFS) in Syria and Lebanon provide key constraints on slip rates and earthquake histories along this continental transform plate boundary between the Arabian and African plates. Additionally, InSAR helps constrain late Cenozoic tectonics by providing high-resolution DEMs for geomorphic analyses, as well as short-term deformation that complements GPS measurements. The left-lateral DSFS in this region comprises two general segments: A large restraining bend in Lebanon and southwestern Syria, and a structurally simpler, north-south striking segment in northwestern Syria. Within this “Lebanese Restraining Bend” (LRB), crustal deformation involves a system of regional strain partitioning between strike-slip faults and compressional structures parallel to these faults. North of the LRB, uplift and horizontal shortening (in addition to strike-slip displacement) continue perpendicular to the transform (with extension localized to strike-slip step-overs); this probably reflects a northward increase in convergence between the Arabian and African plates, as suggested by regional plate tectonic models. Combined with historical records of large earthquakes that span several millennia, paleoseismology elucidates the temporal and spatial patterns of large earthquakes. In some cases, historical observations are ambiguous about the culprit structures, but this can be distinguished based on paleoseismology. Within the LRB, historical records suggest a sequence of 4 major earthquakes that occurred within the region of southwestern Syria and Lebanon during the 18th and 19th centuries. North of the LRB (i.e., in northwestern Syria), a north-to-south sequence involving at least 3 major earthquakes appears to have occurred during the 11th and 12th centuries, after which this region has experienced nearly 800 years of seismic quiescence. Using the available information on these events from paleoseismic and historical data, we explore the implications of this apparent sequence in terms of possible fault interactions. These results demonstrate the importance of scenarios involving multiple seismogenic structures proximal to the metropolitan centers of Damascus and Beirut for regional earthquake hazard assessments.