Measuring interseismic deformation of the Dead Sea fault from along-track Sentinel-1 TOPS interferometry

Abstract

<p>The north-south component of ground deformation remains difficult to derive from InSAR due to the limited sensitivity of standard InSAR observations in that direction. The new approach of burst-overlap interferometry (BOI) exploits swath overlaps of the Sentinel-1 TOPS acquisition mode to retrieve accurate north-south displacements. We applied time-series analysis to such along-track BOI observations of the roughly north-trending Dead Sea fault. Using a large number of Sentinel-1 images acquired from both ascending and descending tracks, we retrieved the horizontal displacement in the burst-overlap areas. Mis-registration errors caused by orbit errors, timing errors, or tropospheric delays are limited in burst-overlap velocities, and ionospheric delays can be reduced through spatial averaging, enhancing the surface displacement estimation. However, interferometric decorrelation is a challenge, as it degrades the co-registration performance in addition leading to fewer observations, particularly near the northern Dead Sea fault. By exploiting hundreds of images, we find a clear and consistent velocity change across different segments of the Dead Sea fault, using coherent distributed scatters optimized by integrating temporal coherence. Modeling of the ascending and descending BOI velocity results suggests that the fault-parallel velocity is in the range 4.2-5.0 mm/yr south of the Lebanese restraining bend, whereas only about half of that to the north of it. The results demonstrate the applicability of BOI time-series analysis in medium-to-low coherence regions with low deformation rates.</p>