Inversion of the wideband high-frequency electromagnetic data

To estimate the underground resistivity and permittivity, the nonlinear leastsquares inverse method based on Monte-Carlo algorithms is applied in this paper to inverse the ellipse polarization data of wideband high-frequency electromagnetic (WHFEM) method. From the inversion cases, the nonlinear least-squares inverse method can execute well in the half-space or two layer earth. In order to reduce to unstable and increase convergence, the Monte-Carlo algorithm is used for multiple layers model. In the second part, we also adopt the phasor vectorgraph method for fast inversion of apparent resistivity and permittivity which is helpful to geology mapping or initialization for the least-squares inversion.