Dimensionality and directionality analysis of the magnetotelluric data along the coastal part of western Saurashtra, Gujarat

The Magnetotelluric (MT) data from 14 MT stations along a NW-SE profile, having a length of 40 km, is processed for a period range of 0.01-100s along the coastal part of north-western Saurashtra, India to estimate the dimensionality of the MT data, using three different approaches, that is, Phase Tensor (PT) technique, WALDIM code, Swift's and Bahr's Skew technique. The Swift's and Bahr's skew result suggests 1D structure for low periods (0.01-1 s) and 2D structure for high periods (1-100 s), except for some sites which show a 3D subsurface structure for high periods (1-100 s). The results generated through PT and WALDIM code are consistent with those from Swift's and Bahr's skew technique. The strike estimated through Phase Tensor (PT), Groom-Bailey (GB) and Becken and Burkhardt (BB) technique for broad period 0.01-100s suggest NNE-SSW regional strike direction, which is well correlated with the Delhi-Aravalli tectonic trend. From the 1D inverse model, the Quaternary and Tertiary sediments are found up to the depth of 300-400m followed by Deccan Trap. A conductive zone (having resistivity <20 Ohm-m) in the central part of the profile near Okha Rann is also observed which suggests the presence of a fault.