InSAR observation of the strike-slip faults in the northwest Himalayan frontal thrust system

The Indo-Asian collision formed a series of north-dipping Cenozoic thrust faults in the Himalayan region, some of which are still active. The frontal thrust system in the northwest Himalayas has significant lateral variation, with the appearance of a reentrant along the thrust front. In the transfer zone of the structural reentrant, strike-slip faults dominate the deformation. To better understand the activities of the strike-slip faults in the northwest Himalayan frontal thrust system, interferometric synthetic aperture radar (InSAR) was used to measure the slip rate and direction. Radar image pairs with long time intervals are preferred to monitor the cumulative displacement caused by a low slip rate along the faults. The measurement across the Kalabagh fault zone indicates that ongoing slip rates are lower than those previously measured by conventional methods. The activities along the Kalabagh fault have segmental characteristics. Current deformation at the north segment mainly concentrates on the splay faults east of the Kalabagh fault. The southward decrease of displacement in the eastern fault block suggests that active deformation is mostly accumulated within the Potwar Plateau-Salt Range thrust wedge instead of at the thrust front. This work indicates that the Kalabagh fault zone linking the thrust fronts of the Salt Range and the Surghar Range plays an important role in accommodating the deformation in the Himalayan frontal thrust system caused by the Indo-Asian convergence.