A magnetotelluric (MT) study across the Koyna seismic zone, western India: evidence for block structure

Wide band magnetotelluric measurements were carried out at 16 sites along Guhaghar–Sangole traverse across the Koyna seismicity zone. The results of the study, besides providing details of Deccan trap thickness variation along the traverse, brought out several structural characteristics of the subsurface extending to deep crustal levels. The Koyna fault zone is characterized by a weak expression of a moderately conductive feature extending only up to a depth of 4–5 km. Two-dimensional modeling results bring out distinct block structure in the Koyna region and are compared with velocity and density structure of the region. The deep electrical structure is interpreted in terms of lateral lithological heterogeneities.