Surface deformation and geometry of the Himalayan frontal thrust system in Pakistan: An insight from InSAR and seismic interpretation

This research evaluated the current rate of surface deformation in the Western Himalayas, focusing on the western Salt Range and the Trans Indus Ranges. The study focused on identifying the presence of a ductile detachment and its correlation with seismic activity. We utilized the InSAR-SBAS (small baseline subset) method and 2D reflection seismic interpretation to analyze 2937 Sentinel-1 A interferograms collected from 2017 to 2023. The findings indicate that the western Salt Range, Kalabagh Fault, and Marwat-Khisor Ranges (Bannu Basin) are currently experiencing aseismic creep, with average surface deformation rates of 6 mm/year, 5.5 mm/year, and 7.6 mm/year, respectively. Interestingly, no surface deformation was observed in the Surghar Range front, although seismicity is mainly concentrated in the Kohat Fold-Thrust Belt. Despite experiencing a 5.2 Mw earthquake in 2018, the Kurram thrust does not show any surface deformation. The Global Navigation Satellite Systems (GNSS)-derived movement rates for the Salt Range and Kalabagh Fault align with the InSAR results. We also found that the presence of a single regional detachment (Precambrian Salt Range Formation) facilitates the aseismic movement of the Potwar and Bannu thrust sheet over the Punjab Foreland region, in contrast to the multiple detachments in the Kohat Fold-Thrust Belt.