Fault delineation study using soil–gas method in the Dharamsala area, NW Himalayas, India

Soil–gas activity in the vicinity of neotectonic fault zones within the Dharamsala area in the region of the NW Himalayas, India, has been investigated by determining enhanced concentration values of radon and helium in the soil, using an ionization chamber and an ASM 100 HDS (Alcatel), respectively. A geological map of the area was used for site selection and to locate the predicted courses of faults. Elevated levels of radon and helium in the soil gas were found along a profile of a major fault (MBT-2). Radon shows variation not only due to the tectonic structures but also due to change in lithology. Helium and radon anomalies together show that apart from conspicuous thrust MBT-2, the area under study is cut across by the N-S transverse faults/lineaments.