Seismotectonics of the great 1905 Kangra earthquake meizoseismal region in Kangra–Chamba, NW Himalaya

Abstract

Three great earthquakes with magnitude greater than 8 have struck the Himalayan belt within a span of 50 years, and the 1905 Kangra earthquake is one of them. The seismotectonics of the meizoseismal region of this earthquake in the Kangra–Chamba region are analyzed on the basis of the major structures and the present day seismic activity. The microseismicity recorded by a network of 12 stations for a period of 16 months spanning 4 years (1993–1996) shows the activity is mainly concentrated over the Main Boundary Thrust (MBT) and Panjal Thrust (PT) zones and the Chamba Nappe region. A NE–SW vertical section reveals that the majority of events are concentrated within a depth range of 5 to 18 km, and the majority of the foci lie between 12 and 18 km. The base of the microseismicity zone is interpreted as representing a contact or a decollement plane between the top of the Indian plate and the Himalayan rock formations. This decollement plane is interpreted as the northern continuation of the detachment observed in the sub-Himalaya in reflection profile. The southward propagation of the Chamba Nappe, as well as the PT and MBT zones, over the detachment causes accumulation of strain energy in this region.