DEEP ELECTRICAL-CONDUCTIVITY STRUCTURE BENEATH THE SOUTHERN PART OF THE INDO-GANGETIC PLAINS

Analysis of magnetotelluric data near the southern boundary of the Indo-gangetic basin reveals a clear two-dimensional structure. Two-dimensional numerical modelling of the data has been carried out; the E-polarization response is found to be very similar to the local one-dimensional response. A study has been carried out to remove the screening effect on the magnetotelluric data caused by the top layer sediments. After the removal of the top layer sediments, a best fit model of the averaged magnetotelluric field data has been found, which has a very thick resistive upper crust and a conducting lower crust. The conductance of the lower crust is found to be much less than the values of lower crustal conductance obtained in Eastern Siberia. In contrast, the upper mantle below the Indo-gangetic plains has a resistivity significantly greater than that of the upper mantle below Eastern Siberia.