Tectono-Geomorphic Studies along the Khetpurali Taksal Fault, Northwestern Himalayas

The Northwestern Himalayas have been host to many earthquakes, with the recent 1905 Kangra Mw 7.8. Studies suggest the seismic gap in the Northwestern Himalayas to be more than Mw 7.8 in general, and of about Mw 8.4 in the Nahan region of the Northwestern Himalayas. There are studies suggesting the rupture of the Himalayan Frontal Thrust (HFT) and hinterland subsidiary faults by the Earthquakes in the region. In this study, we focused the Khetpurali Taksal Fault (KTF), which is one of the corroboration. It is an out-of- sequence ~ 250 km long dextral strike-slip fault with an NNW-SSE trend. KTF, which is bounded to the west by the Nahan Salient, and in the east by the Dehradun re-entrant; marks the boundary between the Central Himalayas (convergence rate ~ 18 ± 1 mm/y and obliquity ~0°) and the Northwestern Himalayas (convergence rate ~13.6–14 ± 1 mm/yr and obliquity ~ 15°-30°), which runs through the ~ 100km locked width of the Main Himalayan Trust (MHT). The dextral strike-slip motion has caused the displacement of some quaternary deposits along the KTF. It plays a key role in the slip partitioning between the active thrust and the oblique faults with the HFT displaying the thrusting and oblique component in the Pinjore Garden fault, Jhajra fault, and Barsar fault of the same region in the Northwestern Himalayas. This study is focused on the active fault along the KTF. We prepared the geomorphic map and delineated the extent of the KTF using the high-resolution Cartosat-1 data. Our studies show the presence of displaced terraces, lateral offset of streams, sag ponds, and pressure ridges along the KTF. A displacement of 250m to 1350m has been observed. Samples from the displaced terraces are analyzed by OSL dating technique to find out the slip along the KTF. Understanding the slip along KTF will enhance the understanding of slip partitioning taking place in the Nahan Region as a whole, which will help understand the geodynamics of the region and thus in seismic hazard assessment.