Multi-parameter tomographic inversion for imaging 2D electrical resistivity anisotropy

Resistivity anisotropy is often encountered in practical applications due to different orientations of fractures, joints and crystalline in sedimentary rocks. It may not satisfy assumption of homogenous electrical current flows in all directions that is commonly used in electrical resistivity tomography (ERT). This paper demonstrates nonlinear multi-parameter tomographic inversions for imaging near-surface targets in resistivity anisotropic background rocks, which may be a transversely isotropic or an axial anisotropic rock. Meanwhile, we demonstrate a new data-acquisition array, called ‘full-range gradient’ (FRG) for 2D ERT. FRG is an enhanced version of the common gradient measurement. We conducted synthetic experiments of the multi-parameter tomographic inversions to exam the capability of the new data-acquisition array and compare the imaging results with the traditional dipole-dipole and common gradient arrays. Our results show that FRG provides an alternative to the traditional electrode arrays and the common gradient measurement and may yield competitive subsurface images to any other electrode arrays.