ELECTROMAGNETIC RESPONSE OF HORIZONTAL MAGNETIC DIPOLE OVER INHOMOGENEOUS EARTH MODEL WITH LINEAR CONDUCTIVITY VARIATION

The problem of calculating the electromagnetic (em) field response of a horizontal magnetic dipole placed over a multi layer earth model wit h 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 intermediat e transition layer, for the case of quasi-static approximation. Comput ations are performed for the absolute-amplitude ratio, i.e. the ratio of the absolute amplitude of the field component over a multi-layer mo del and the corresponding component over a homogeneous half space poss essing the conductivity of the top layer. The effects of transition la yer thickness and conductivity contrast between the top and bottom lay ers are investigated by computing these ratios as a function of numeri cal distance. The results depict characteristic dependence of the em r esponse on conductivity inhomogeneity.