Geomorphological and seismological investigations in a part of western Kumaun Himalaya, Uttarakhand, India

The Kumaun Himalaya in India is seismotectonically one of the most responsive sectors of the Himalayan arc. The region falls in the seismic gap and is frequently rocked by the earthquakes of low to medium magnitude. In the present investigation, the seismic data of the area were obtained by deploying a seismic network, and an attempt is made to interpret the seismological data of the local events and their relation with the geomorphology and thrusts/faults rejuvenation. The epicentral distribution of the earthquakes defines a relatively narrow zone of seismicity. A majority of earthquakes are confined to shallow depth with low stress drop and higher peak ground velocity (PGV). Further, the neotectonic investigations along the major river valleys indicate the neotectonic activity in the form of paired and unpaired terraces, shifting of river courses, fault scarps, development of palaeolakes, straightening of river channels, and deep cut V-shaped valleys. From the geomorphological and seismological data, the thrust and fault systems in the area are seismotectonically quite active even today. Some of the transverse faults — viz. Dwarahat-Chaukhutia fault, Takula-Basauli fault (Sim Gad valley), Tilora-Jyala fault (Kosi valley) — show spectacular tectonic landforms and seismicity. As a matter of fact, the NNW/NW–SSE/SE trending faults are active in the region.