North‐South Shear Along the West‐Lut Fault, Iran, Imaged From Burst Overlap InSAR

Abstract High‐resolution geodetic measurements of crustal deformation from InSAR provide crucial constraints on a region's tectonics, geodynamics, and seismic hazard. However, space‐based InSAR usually only provides good constraints on horizontal displacement in the east‐west direction, with the north‐south component typically provided by low‐resolution GNSS measurements. Sentinel‐1 has the potential to provide measurements that are sensitive to north‐south motion through the exploitation of the burst overlap areas produced by the TOPS acquisition mode, although noise contributions from surface decorrelation and signal propagation perturbations through the ionosphere make it challenging to detect surface displacements associated with interseismic deformation with millimeter per year accuracy. Here, we demonstrate a time‐series approach to burst overlap interferometry appropriate for extracting subtle long‐term displacements. Our approach includes mitigation of ionospheric noise, and we investigate different filtering approaches to optimize the reduction of decorrelation noise. We apply our approach to estimate the mean ground velocity in the azimuth direction from data acquired between 2014 and 2019 along the West‐Lut Fault, a north‐south striking active fault in eastern Iran. Our results agree well with independent GNSS measurements, but the denser coverage of the technique allows us to detect the variation in strain accumulation between the northern and southern segments of the fault. Simple modeling indicates a variation in slip rate from 7.4 0.4 mm/yr in the south to 4.2 0.5 mm/yr in the north. With current efforts to use InSAR to constrain strain rates globally, along‐track measurements can fill a crucial gap in north‐south sensitivity.