InSAR Observation of the Strike Slip Faults in the NW Himalayan Frontal Thrust System

The Indo-Asian collision formed a series of north-dipping Cenozoic thrust faults, some of which are still active, in the Himalayan region. The frontal thrust system in NW Himalayas has significant lateral variation with the appearance of wrenched topography in areas where strike slip faults dominate the deformation. To better understand the activities of the strike slip faults in the NW Himalayan frontal thrust system, Interferometric Synthetic Aperture Radar (InSAR) was used to measure the slip rate and direction of the strike slip faults. It has the capability of estimating surface displacement at centimeter scale. Due to the low slip rate (<10 mm/yr) of these faults and the noise between radar image pairs, it is difficult to extract reliable displacement values from single interferogram. Therefore, unwrapped interferograms were stacked to reduce the short wavelength noise including tropospheric phase delay. Stacking results are in terms of average rate per year. The measurements across the Kalabagh strike slip fault indicate that ongoing slip rates are lower than the previous measurement by conventional methods. The activities along the Kalabagh fault have segmental characteristics. Current deformation at the north segment mainly concentrates on the Dinghot fault, a branch of the Kalabagh fault. The differential vertical displacement at two sides of the fault suggests that oblique transpressional slip have significant influence on the deformation along the strike slip faults. The Kalabagh fault zone linking the thrust fronts of the Salt range and the Surghar-Shinghar range plays an important role in accommodating the Indian-Asian convergence in this area.