Seismic Hazard and seismogenesis in Kashmir Himalaya

The convergence of the Indian and Eurasian plates is accommodated through stick and slip on the detachment or Main Himalayan Thrust (MHT). The part of the MHT that lies under the Outer and Lesser Himalaya is seismogenic and slips episodically and accumulates strain during the interseismic period when it is locked, which is released during the earthquakes through sudden slip on the MHT. The MHT further north slips aseismically. Out of the three known seismic gaps (Kashmir gap, Central gap, Assam gap), we report results of GPS measurements from Jammu-Kashmir region. The 250 km long segment of the Kashmir Himalaya, known as the Kashmir Seismic Gap, has not experienced a major earthquake since 1555, although a possible event of magnitude Mw ~6 was recorded west of Srinagar in 1885. This region appears to be an anomaly, as the width of the Main Himalayan Thrust (MHT) is suggested to exceed 160–170 km compared to a width of approximately 100 km in other parts of the Himalaya. The seismic activity in the Kashmir region is diffused and does not indicate the location of the locking line. Additionally, the 3,500-meter contour, which encircles the Kashmir Valley and extends to the Pir Panjal and Zanskar Himalayas, does not guide its position either. We analysed GNSS data from 22 sites along with the published   data from the region. To assess the convergence in the Jammu-Kashmir region, we examined two arc-normal profiles. Assuming the MHT extends to the Main Frontal Thrust (MFT) and that strain accumulation is uniform in the locked shallow MHT, we estimated the locking width in the Kashmir region (Profile-1) to be 169 ± 10 km, with a total convergence rate of 13.7 ± 1 mm/yr. Similarly, in the Jammu-Himachal region (Profile-2), we estimated the locking zone to have a width of 108 ± 10 km with a total convergence rate of 17.8 ± 1 mm/yr. The spatial variation of locking in the Kashmir and Jammu-Himachal regions shows high coupling. The Kashmir region's intermontane valley demonstrates lower coupling than surrounding high-coupling zones. While both areas show strain accumulation, the deformation and convergence in the Kashmir Himalaya are more distributed compared to the central Himalaya.