Earthquake Swarms and Seismic Gaps Along the Dead Sea Fault System

The appearance of seismic sequences along fault zones provides paramount information regarding faulting characteristics and tectonic kinematics, especially for microseismic activity along plates with relatively slow motion. Moreover, the characterization of seismic sequences can shed light on the mechanisms triggering the seismic activity. This study examines the seismicity along the Dead Sea fault system, a ∼400 km strike-slip plate boundary between the Arabian and Sinai subplates. Earthquake clusters and background seismicity are defined by applying a nearest-neighborhood algorithm to a relocated catalog from 1983 to 2023. We recognize 56 clusters above the magnitude of completeness, which are classified into four types: aftershock sequences, doublets or triplets, and swarms. Aftershock clusters have a magnitude difference greater than 0.5 between the largest and second-largest events in the cluster. Doublets and triplets feature similar magnitudes among their two or three largest events, respectively. Swarms are clusters for which the magnitude difference is less than 0.5 between the four largest events. Our statistical analysis indicates certain spatial tendencies of the cluster-type distribution along the Dead Sea fault. Aftershock type clusters are mostly located along the Dead Sea basin (for which only 22% of clusters are classified as swarms), and swarms are recognized north and south of it: the Arava fault (south), the Jordan Valley fault, and the Sea of Galilee (north). A spatial correlation emerges between earthquake swarms and regions of relative seismicity quiescence (gaps), for which swarms develop at the edges of the seismic gaps. The seismogenic depth associated with aftershock populations shows con-siderable variability: In the northern segment, clustered events occur mostly at the shallow 16 km depth, whereas in the southern segments, most clusters are located deeper, reaching 24 km depth. These observations are consistent with the shallower seismogenic depth measured in these segments.