Recent years, three-dimensional magnetotelluric (MT) inversion is widely used in geophysical structural surveys. In this paper, we show how to galvanic distortion would influence to 3-D MT inversion results, and would like to propose an improvement of model covariance matrix which could deal the galvanic distortion. For accommodating the galvanic distortion effects, we first simulate a set of synthetic MT response for some models and then add the distortion effects that are a function of

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... tion locations. We applied WSINV3DMT as an inversion method to these synthetic MT responses. As a result, we confirmed distinct differences between 3-D MT inversion results depending on the degree of galvanic distortion. When we applied WSINV3DMT with the modified model covariance matrix, we obtained better inversion result. Based on these numerical experiments, we conclude that the galvanic distortion should be considered and be dealt with in the inversion.