Electromagnetic response of horizontal magnetic dipole over inhomogeneous earth model with linear conductivity variation

Abstract

The problem of calculating the electromagnetic (em) field response of a horizontal magnetic dipole placed over a multi layer earth model with one of the layers having linear variation of conductivity with depth is formulated. Analytical solutions are obtained for the three layer earth model having linear variation of conductivity in the intermediate transition layer, for the case of quasi-static approximation. Computations are performed for the absolute-amplitude ratio, i.e. the ratio of the absolute amplitude of the field component over a multi-layer model and the corresponding component over a homogeneous half space possessing the conductivity of the top layer. The effects of transition layer thickness and conductivity contrast between the top and bottom layers are investigated by computing these ratios as a function of numerical distance. The results depict characteristic dependence of the em response on conductivity inhomogeneity.