Earthquake Activity in Kishtwar –Dharamshala Region of North-West Himalaya

In the present study, Kishtwar-Dharamshala region of north-west Himalaya that experienced about 30 earthquakes in last three years having magnitudes between 4.0 to 5.8 has been studied. This region falls in zone IV according to the Seismic Zoning map of India and marked with number of regional and local thrusts faults. This region experienced around 476earthquakes during last 30 years as per records available at Indian Metrological Department. Out of these 476 events around 321 earthquakes have magnitude less than 3.0 and only 7 earthquakes experienced for which the magnitude lies in between 5.0-6.0. The maximum magnitude recorded in this region which was reported by IMD is M5.8 on 1stMay 2013 followed by number of aftershocks. The earthquakes occurred in last 3 years are mainly concentrated in Kishtwar zone and Dharamshala zone about 100 km apart from each other. This activity in Kishtwar spans about 60 km in width and is confined between MBT and MCT. The activity starts at 9 km in depth and extended down 60 km depth in Kishtwar region. While in Dharamshala region this activity is scattered near MBT, spans about 45 km in width and extended below from 10 km to 40 km down in the crust. The stress drops associated with earthquakes in Kishtwar zone varies between 5.8 MPa and 13.0 MPa and for Dharamshala zone between 3.2 MPa and 13.3 MPa.The stress drops observed in these regions are similar to other parts of Himalaya. The average stress drops associated with Himalayan earthquakes are of the order of about 6.0MPa (Kumar et al., 2008; Kumar, 2011). Hence the stress drops associated with these earthquakes doesn’t reflect any abnormal behavior. The distribution of this earthquake activity shows the presence of active faults in these regions. As geological processes generally took time of hundred years to occur, so nothing can be inferred about when it will rupture with the available analyzed data. A close monitoring of earthquake activity in these regions is required.