Electrical resistivity tomography along the Himalayan Frontal Thrust in the northwestern Frontal Himalaya for active tectonics studies

Abstract

Dependence of ground resistivity upon mineral content, porosity, degree of water saturation in the rock and fluid content makes it ideal for imaging and understanding the subsurface. Results of resistivity imaging, used for active tectonics studies at Kala Amb region in the northwestern Frontal Himalaya are discussed. Study area is selected across the exposed section of the Himalayan Frontal Thrust based on a previous trench excavation survey. An electrical resistivity tomography 2D profile survey is conducted along two lines in Kala Amb region. The lines are selected with the primary objective of extending the features identified in the trench section into the subsurface. The study found to be helpful in understanding the efficacy of this method for the recognition and geometrical characterisation of faults across morphotectonic scarps or fault traces in a region which experienced late Quaternary tectonic activity. The inverted resistivity model has lateral and vertical resistivity variations according to different depositional units in the area. The presence of a north dipping fault at 54-m distance from zero electrode position towards south clearly distinguishes two separate lithological units. The liquefaction feature identified on the trench wall section which is also inferred from the resistivity section appears to be originated from greater depth. Similarity of resistivity features and spatial distance of two profiles allow us to interpret the lateral continuity of subsurface features and to identify the thickness of Quaternary deposit over river bed level.