Linear source CSAMT response simulation in the 2D anisotropic formation with topography

Electrical anisotropy and topography are important factors affecting the distribution of electromagnetic fields. Therefore, it is necessary to study the response of controlled source electromagnetic fields to electrical anisotropic topography. In this study, a two-dimensional anisotropic geological model with topography was designed and the finite element method was used to calculate the electromagnetic field response of a Controlled Source Audio-frequency Magnetotelluric (CSAMT) line source. It was found that not only were the apparent resistivity and phase curves sensitive to anisotropic characteristics, but topography also exerted a significant influence on electromagnetic field distribution. Moreover, upper convex topography had a greater influence on electromagnetic response than lower concave topography. Therefore, topographic correction or the use of anisotropic models for data processing and interpretation should be considered in areas with extreme topography or prominent anisotropy. Results from the present study may help guide field applications of the CSAMT method and improve the theoretical and practical utility of the controlled source electromagnetic method. •If anisotropic medium is treated by isotropic theory, both the apparent resistivity and impedance phase will be distorted.•The influence of the convex shape topography is more severely than that of the concave shape topography.•Both anisotropy and topography have effect on CSAMT, and this effect is more complicated when the two effect mixed together.