[S-EM14] Electric, magnetic and electromagnetic survey technologies and scientific achievements

[SEM14-P06] Distortion decomposition of MT impedance tensors in 1D anisotropic media

*Tianyi Dai¹, Yuguo Li¹ (1.Ocean University of China)

Keywords:Magnetotelluric, Electromagnetic field, Distortion decomposition, Electrical anisotropy

The electromagnetic local distortions due to shallow local small-scale inhomogeneities are the major problem for accurate interpretation of Magnetotelluric (MT) data. These distortions can be galvanic and inductive. Decomposition techniques of MT impedance tensor that only consider galvanic distortion and ignore inductive distortion have been well developed, under the assumption that subsurface electrical structures are electrically isotropic. In this paper, we present a decomposition method of MT impedance tensors in 1D conductivity anisotropic media, in which both the electric field galvanic distortion and the associated magnetic distortion are taken into consideration. Regional anisotropic responses and electromagnetic distortion parameters are recovered by using the Quasi-Newton BFGS algorithm with the aid of phase tensor analysis and trust region method. The model studies indicate that the inclusion of magnetic galvanic distortion in conventional decomposition of MT impedance tensors is necessary and essential for subsequent procedures. The decomposition method is also employed in the processing of BC87 data set, demonstrating the significance of considering regional electric anisotropy.