The Effect of Inhomogeneous Magnetic Permeability on Magnetotelluric Responses: 1D and 2D Models

—When solving direct and inverse problems of magnetotellurics, magnetic permeability throughout model medium is conventionally assumed to be constant and equal to vacuum permeability. To study the effect of anomalous magnetic properties of rocks on magnetotelluric data, a collection of one- (1D) and two-dimensional (2D) simulation models have been constructed. The equivalence principle for horizontally layered sections which takes into account magnetic permeability of layers is demonstrated. It is shown how the components of transfer operators—impedance, tipper, telluric and horizontal magnetic tensors—change depending on the permeability of a local conductive body. The results of the 2D inversion that excludes inhomogeneity in magnetic properties of the medium are presented for synthetic data. It is shown that at the values of relative magnetic permeability above 2, the inversion may markedly overestimate the depth to the top edge, the thickness, and electrical resistivity of the considered structures.