Distortion can be as little as a simple vertical shifting of apparent resistivity sounding curves.
At worst, there is a mixing of the regional tensor response elements because of uncertain tensor rotation that produces both amplitude and phase distortion. In practice, a low frequency assumption is usually invoked wherein the skin depths inside and outside the inhomogeneities are large compared to the size of the scatterer. This results in a neglect of magnetic galvanic distortion and produces real, frequency-independent distortion tensor elements. They confirm that the inclusion of local magnetic fields created by galvanically distorted currents produce complex, frequency dependent distortion. Thus, magnetic galvanic distortion can change both the magnitudes and phases of the observed MT response.