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

[SEM14-05] Application of Electromagnetic Wave Propagation Theory to the Magnetotelluric: Take the Dipping Interface Model as an Example

*Guihang Shao^1,2, Yuguo Li², Jie Lu², Yunju Wu² (1.Shandong Provincial Research Institute of Coal Geology Planning and Exploration, 2.Ocean University of China)

Keywords:Magnetotelluric, Electromagnetic wave propagation, Complex permittivity, Dipping Interface Model

In magnetotellurics (MT), the theory of electromagnetic wave propagation is often used to understand the propagation process of magnetotelluric fields and the physical meaning of the transfer function. However, MT studies the propagation characteristics of electromagnetic waves in conductive medium, where the electromagnetic field is controlled by the diffusion equation. The analytical expression to accurately describe the propagation mechanism of magnetotelluric waves in the geoelectric model is not available. This paper adopts Born and Wolf’s method of electromagnetic waves in metal [1], and introduces the complex permittivity into Helmholtz’s equations [2]. The analytical expressions are derived for incident wave and reflected wave as well as transmitted wave at a dipping interface. The analytical solutions of MT field are compared with the numerical solution [3], and they agree very well (see Fig. 1).
References
[1] M. Born, E. Wolf, Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light, 7th ed., Cambridge University Press, 1999, pp. 614.
[2] D. Cheng, Field and Wave Electromagnetics, 2nd ed., Tsinghua University Press, 2007, pp. 195-235.
[3] Y. Li. “A finite-element algorithm for electromagnetic induction in two-dimensional anisotropic conductivity structures,” Geophys. J. Int., vol. 148, pp. 389-401, 2002.