Resolving the Slip-Rate Inconsistency of the Northern Dead Sea Fault 

Abstract

Geological studies, GPS observations, and plate motion models consistently show that the slip rate for most of the Dead Sea Fault (DSF) is 4-5 mm/year. However, for the northernmost DSF, just south of where the 2023 Kharamanmaraş earthquakes occurred, results differ, with GPS results from Syria (from before 2010) indicating a lower rate of only 2-3 mm/year. Conventional InSAR observations have not provided useful information about the present-day strain accumulation on the DSF, due to the fault’s north-south orientation and the insensitivity of InSAR to north-south displacements. Therefore, to study this slip-rate inconsistency and overcome limited access to the northern DSF in Syria, we employed time-series analysis of along-track burst-overlap interferometric (BOI) observations from 2014-2021 Sentinel-1 data to retrieve the interseismic horizontal fault-parallel displacements in the burst-overlap areas. Elastic modeling based on the BOI velocities indicates the fault slip rate decreases from ~5 mm/year in the south to only 2.8 mm/year at the northern DSF in Syria, in agreement with the GPS observations. Using what we know about earthquake clustering statistics on the DSF, we also demonstrate that the higher paloseismological slip rate on the northern DSF, which primarily comes from offset markers in the past 3500 years, could by chance be inflated by earthquake clustering. Furthermore, we suggest that the northern Sinai plate, west of the northern DSF is its own micro-plate (Latakia-Tartus plate), separated from the main Sinai plate in the south by a diffuse offshore plate boundary zone between Lebanon the Cyprus arc. This interpretation is supported by elevated offshore seismicity and the several moment tensor solutions we could determine. Together, our results resolve the long-standing slip-rate inconsistency along the northern DSF and indicate lower earthquake hazard for that part of the fault than previously thought.