Quantitative interpretation of geomagnetic induction response across the thrust zones of the Himalaya along the Ganga-Yamuna Valley

Abstract

Geomagnetic variations, recorded through a two-phase magnetovariational study carried out along the Ganga-Yamuna valley of the Garhwal Himalaya, northwest India, are reduced to a set of induction arrows spanning a period range of 12-128 minutes. The spatial behaviour of induction response indicates that the Main Frontal Thrust is a major electrical discontinuity with enhanced conductivity to the south, beneath the Indo-Gangetic plains. A full 2-D electrical resistivity model which reproduces the observed electromagnetic response, essentially requires a highly conducting layer at mid-crustal depth beneath the Indo-Gangetic Plains, becoming less conducting on underthrusting beneath the frontal Himalayan belt. This layer coincides with the brittle-to-ductile transition zone along which lie the foci of most moderate earthquakes. -from Authors