A comparison of the results of 2D anisotropic DC resistivity inversion with 1D joint DC resistivity and CSRMT inversion

In the Eastern Ghats Mobile Belt of Odisha, India, the interpretation of sub-surface resistivity using the direct current (DC) resistivity method can be enhanced by considering the inherent anisotropy of the Precambrian gneissic basement. To investigate this, two-dimensional resistivity and far-field controlled-source radiomagnetotelluric (CSRMT) data were collected in the area. A newly developed 2D code was used to perform anisotropic inversion of the 2D resistivity data, which was validated by the satisfactory model parameter reconstruction for synthetic data before inverting the field data. To ascertain the accuracy of the newly developed 2D code, the joint 1D inversion of a galvanic DC resistivity sounding and an inductive CSRMT method was carried out, a standard approach for estimating the subsurface anisotropy. The results of the joint DC-CSRMT inversion were compared with the 2D anisotropic DC resistivity sections. It was observed that the anisotropy obtained by the joint inversion was higher than that reported by 2D anisotropic DC resistivity, particularly in the layers corresponding to the fractured zone and below in the borehole. To verify the authenticity of the 1D inversion, the importance, damping parameters, and V-matrix of parameters obtained from singular value decomposition analysis were also analyzed.