Influence of a magnetically permeable surface layer on transient electromagnetic field of a vertical magnetic dipole on a two-layer conducting earth

The transient electromagnetic field, in the frequency domain, on a two-layered conducting earth is reexamined when the usually neglected magnetic permeability contrast is considered. It is shown that for two-layered earth model, where the upper is permeable, the electromagnetic induction response is modified over the nonpermeable case. It is obtained as a summation of waveguide modes plus contributions from branch-cuts in the complex plane of the longitudinal wave number. The results from this paper can be used to evaluate numerical solution of other more complicated forward modeling algorithms. It can also be used in developing fast and simple interpretation tools, which can deliver quick estimation of the earth structure at the field.