Two-Dimensional Magnetotelluric Forward Research for the Vertical Anisotropy

Huan  Ma; Mao  Wang; Han-Dong  Tan; Miao-Xin  Yang

doi:10.4236/ijg.2015.610091

Miao-Xin Yang, Han-Dong Tan, Mao Wang, Huan Ma

Abstract: When we study and process magnetotelluric data, the earth's interior structure is usually equated with isotropic medium in the existing approaches. When the underground structure is complex, there is serious resistivity anisotropy in macroscopic view, and then the traditional processing and interpretation methods often produce wrong results. For that we must establish the study method based on the anisotropy in order to explain the measured data exactly. In this paper, by considering the change of resistivity in three electrical spindle directions, we deduce two-dimensional magnetotelluric variational equation for vertical anisotropy. The study region is divided into many rectangular units, and it is dealt with linear interpolation in each of them. By comparing with former achievements including the results of the isotropic and anisotropic models, it demonstrates the validity of the program. The pseudosection map of vertical anisotropic body shows that we can’t ignore the anisotropy effect and provides a solid foundation for the further inversion study.

Keywords: Vertical Anisotropy, Magnetotelluric Method, Isotropy, Anisotropy Effect

Cite this paper: Yang, M. , Tan, H. , Wang, M. and Ma, H. (2015) Two-Dimensional Magnetotelluric Forward Research for the Vertical Anisotropy. International Journal of Geosciences, 6, 1166-1172. doi: 10.4236/ijg.2015.610091.

References

[1] Reddy, I.K. and Rankin, D. (1975) Magnetotelluric Response of Laterlly Inhomogeneous and Anisotropic Media. Geophysics, 40, 1035-1045. http://dx.doi.org/10.1190/1.1440579

[2] Key, K. and Weiss, C. (2006) Adaptive Finite Element Modeling Using Unstructured Grids: the 2D Magnetotelluric Example. Geophysics, 71, G291-G299. http://dx.doi.org/10.1190/1.2348091

[3] Liu, Y. and Wang, X.B. (2010) FEM Using Adaptive Topography in 2D MT Forward Modeling. Seismology and geology, 32, 382-391. (In Chinese)

[4] Xu, S.Z. and Zhao, S.K. (1985) Solution of Magnetotelluric Field Equations for a Two-Dimensional, Anisotropic Geoelectric Section by the Finite Element Method. Acta Seismologica Sinaca, 7, 80-90. (In Chinese)

[5] Yang, C.F. (1997) MT Numerical Simulation of Symmetrically 2-D Anisotropic Media Based on the Finite Element Method. Northwestern Seismological Journal, 19, 27-33. (In Chinese)

[6] Li, Y. (2002) A Finite-Element Algorithm for Electromagnetic Induction in Two-Dimensional Anisotropic Conductivity Structures. Geophysical Journal International, 148, 389-401.
http://dx.doi.org/10.1046/j.1365-246x.2002.01570.x

[7] Pek, J. and Verner, T. (1997) Finite-Difference Modeling of Magnetotelluric Fields in Two-Dimensional Anisotropic Media. Geophysical Journal International, 128, 505-521.
http://dx.doi.org/10.1111/j.1365-246X.1997.tb05314.x

[8] Huo, G.P., Hu, X.Y. and Liu, M. (2011) Review of the Forward Modeling of Magnetotelluric in the Anisotropy Medium Research. Progress in Geophysics, 26, 1976-1982. (In Chinese)

[9] Hu, X.Y., Huo, G.P., Gao, R., et al. (2013) The Magnetotelluric Anisotropic Two-Dimensional Simulation and Case Analysis. Chinese Journal of Geophysics, 56, 4268-4277. (In Chinese)

[10] Huo, G.P. (2012) Numerical Modeling of Magnetotelluric Fields in Two-Dimensional Anisotropic Media. Ph.D. Thesis, China University of Geosciences, Wuhan.

[11] Qin, L.J. (2013) The Forward and Inversion of MT Field in Anisotropic Conductivity Structures. Ph.D. Thesis, Zhejiang University, Hangzhou.