High Resolution Interseismic Deformation of the Southern Dead Sea Transform Fault

We investigate interseismic deformation in the region of the southern Dead Sea Transform Fault, bordering Saudi Arabia and Jordan to the east, and Egypt and Israel to the west. This region has experienced several major earthquakes, most recently the Mw 7.2 1995 Nuweiba earthquake offshore of the Gulf of Aqaba. Previous geodetic studies use burst-overlap interferometry and campaign GPS to constrain present-day kinematics and elastic strain accumulation. These data suggest variations of interseismic velocity, which are interpreted by standard screw dislocation models with the fault locking depth decreasing from north to south. The sparsity of the data challenges estimates of model uncertainties and parameter correlations. Here, we explore high-spatial resolution deformation measurements stretching over several hundred kilometers and their role in improving constraints of fault model parameters.

To image the deformation field across the wide plate boundary, we construct dense InSAR time series using multiple parallel tracks of both ascending and descending Sentinel-1 acquisitions, spanning from late 2014 to 2022. The small interseismic tectonic motion of ~5 mm/year along the nearly north-south striking transform fault is challenging to measure with our imaging geometry (equivalent to observing <2 mm/year of slant-range change in the ascending track). Thus, it is important to compensate for non-tectonic long-wavelength signals that may dominate the measurements, including the atmospheric signals, the solid Earth tides, and the impact of plate motion.

We demonstrate that the primary biases to the long-wavelength InSAR deformation are the ionospheric apparent velocity over long-term solar cycles and a cm-per-year scale spatial ramp resulting from the bulk Arabian plate motion in the satellite's orbital reference frame. The final corrected secular velocity field shows continuous interseismic strain across the fault with sub-mm/year scatter and is consistent with previous locking models with decreasing locking depths southward to the Gulf of Aqaba. In order to eventually develop a refined fault model, we also explore and isolate confounding effects of residual plate motion, as well as hydrological and other processes.