Active Tectonics in the Outer Himalaya: Dating a Landslide Event in the Kumaun Sector

Of the entire Himalayan terrain, the Outer Himalaya is believed to show excellent signatures of active tectonics. The Main Boundary Thrust (MBT) that separates the Outer and Lesser Himalayas has a recorded history of tectonic activities in the recent past. The present study incorporates an additional example of a major landslide event, the Amiyan landslide, associated with the MBT that passes through the toe of this landslide. The Amiyan landslide is one of the biggest debris slides in the Central Himalayan region. Two prominent fault scarps running almost transverse to the MBT have developed during the last 15 years. The slide has been increasing in size at regular intervals from an earlier 0.02 sq km in 1968 to 0.05 sq km till 1992. Thereafter, the process of continuous reactivation of the MBT and the formation of fault scarps has resulted in about 12-fold increase of the slide. Such a topographical adjustment in response to active tectonics in this segment of the Himalaya suggests that the Outer Himalaya is possibly a major locale of present-day stress release in the Himalayan region. The results of this work have significant bearing on the seismotectonic, environmental, ground stability and the related aspects in the Himalayan domain.