Research on DC resistivity for an arbitrarily anisotropic earth using circular scanning measurement

Abstract

This paper presents a 3D forward modelling algorithm with an adaptive finite-element method based on unstructured grids that when used with a circular scanning DC measurement technique can provide an indication of anisotropy in a layered earth. The accuracy of this algorithm is checked against 1D semi-analytical solutions for an arbitrarily anisotropic earth. This anisotropy produces a measurement paradox, results are dependent on the physical relationship between DC transmitter and receiver. To resolve this paradox, a circular scanning measurement technique has been suggested. Through analysing the response of typical anisotropic models, we study the characteristics of apparent resistivity related to the electrically anisotropic media and identification of underground electrical anisotropy. The results of numerical experiments shows the effectiveness of our algorithm and the analysis will be helpful to the interpretation of anisotropic DC resistivity data. Key words: numerical modelling, unstructured grids