Active Fault and Paleoseismological studies in the hinterland region of NW Himalaya

Abstract

The Indian plate is currently underthrusting beneath the Tibetan plateau along the Main Himalayan Thrust (MHT). The strain is getting accumulated during the inter-seismic period on MHT due to this ongoing convergence. The accumulated strain energy is released in a stick-slip fashion on MHT causing destructive earthquakes. Several strong earthquakes within the Himalayan zone have been reported in previous studies such as 1897 at Shillong (Mw 8.2), 1905 at Kangra (Mw 7.8), 1934 at Bihar-Nepal (Mw 8.1), 1950 at Assam (Mw 8.4), 2005 at Muzaffarabad (Mw 7.6), 2015 at Gorkha (Mw 7.8), and 2015 in Afghanistan (Mw 7.6). Based on the distribution of recent and historic earthquake activity in the Himalayas, three seismic gaps can be distinguished from west to east: the Kashmir Seismic Gap (west of the 1905 Kangra earthquake), the Central Seismic Gap (between the 1905 and earthquakes), and the Assam Seismic Gap (between the 1897 and 1950 earthquakes). The major objective of this study is to investigate the hinterland region in the NW Himalaya, which is relatively less explored in terms of its Active Tectonics & Paleoseismology as compared to the deformation front along the Main Himalayan Thrust (MFT). The Nahan salient and Kangra re-entrant are characterised by a complicated pattern of fault distribution which has been proposed in previous studies to get activated, either individually or alongside the Main Frontal thrust, during past large to great-magnitude earthquakes. A detailed tectono-geomorphic map has been prepared using the Cartosat-1 dataset, and geomorphic markers suggestive of recent tectonic activity have been identified in the study region. An exhaustive fieldwork has been conducted, during which a total of 13 samples were collected for Optically Stimulated Luminescence (OSL) dating and Carbon dating to identify signatures of past earthquakes and assess the possibility and degree to which the 1905 earthquake has affected the region. Based on the detailed tectono-geomorphological and paleoseismological investigations, we will be able to assess regional seismic hazards. (*Author RH aka Rukhshar)