Magnetotelluric imaging reveals fragmented crustal blocks beneath the Konkan plains adjoining the Western Ghats, Deccan Volcanic Province, India

Abstract

The Deccan plateau and the Konkan plain of the western continental margin of India are significant morphotectonic features. Seismic activity along with regional-scale geophysical and geological studies suggests that the plateau is tectonically disturbed and the traps together with the sub-basaltic terrain have been experiencing structural deformation along pre-existing linear zones. The recent Palghar swarm activity has drawn significant attention on the crustal architecture of the Konkan plain and the adjoining Western Ghats region. Here, we present the results of a magnetotelluric study carried out along a 100 km long E-W profile traversing major tectonics features between the Konkan plain and the Bhatsa swarm activity region. Two-dimensional modelling of the distortion corrected impedance tensors reveals high resistivity crustal blocks down to 35–40 km dissected by faults/fractures. These crustal blocks are underlain by a moderately conductive mantle lithosphere which is also characterized as a seismic low velocity and low density layer. The persistent elevated topography of the Western Ghats could be explained by a buoyant, low-velocity/low resistivity upper mantle coupled with reactivation of deep crustal features during the Quaternary period. The model yields some westward dipping conductive and resistive zones coinciding with the exhumed topography highs. The west coast fault in the western and the Ghod fault in the eastern part of the profile are imaged as crustal-scale steeply dipping fault zones segmenting the Eastern Dharwar craton (EDC) crust into the EDC1 and the EDC2. The model in conjunction with earlier results from the Palghar swarm activity region suggests southward continuation of the major conductivity anomalies obtained at Palghar. This study proposes that NW extension of the Kurudwadi rift and its interaction with local structural features is possibly affecting the stress state of the region leading to local seismicity.