Abstract:  In the field of electromagnetic detection, skin depth is an important parameter for electromagnetic data analysis and imaging. In practice, the induced field and the polarization field coexist. If the polarization effect of the medium is not considered, there will be obvious errors in the imaging results. In order to solve the above problems, the generalized skin depth formula of the GEMTIP(Generalized Effective-Medium Theory of Induced Polarization) model in the frequency domain is deduced based on the plane wave theory and the GEMTIP model. The accuracy of the generalized skin depth of the GEMTIP model is verified by comparison with the classical skin depth. The generalized skin depth calculation of the GEMTIP model is mainly related to the resistivity and volume fraction. The BP(Back Propagation) neural network inversion method is used to extract parameters. And by constructing a reasonable data sample set, the training error can meet the accuracy requirements, and the mapping relationship between the input and output data is obtained. Several typical three-layer geological model structures are discussed. When the polarization effect is considered, the generalized skin depth formula of the GEMTIP model is verified to improve the identification accuracy of the underground polarized medium. 

Key words: skin depth')">

skin depth, polarization field, neural networks