1-D forward modeling of the CSAMT signal incorporating IP effect
含激电效应的CSAMT一维正演研究

The response of geoelectric objects to frequency domain electromagnetic wave excitation source is the comprehensive response to both electromagnetic induction and induced polarization. Traditionally, the resistivity is considered as a real number parameter unrelated to the frequency when we do the data inversion of CSAMT signal. In fact, the resistivity of polarized layer is a plural number related to the frequency because of the IP effect. In order to promote the research on this comprehensive response, we add the complex-resistivity-models into the CSAMT signal, which will expand the application range of IP method; meanwhile, will improve the accuracy of CSAMT exploration also. Base on Dias-model, this paper studies the forward modeling of IP response with CSAMT 1D layered model of the earth, to provide the theoretical basis for extracting the IP information from CSAMT signal. The study results show that: the amplitude of apparent resistivity and phase curve show obvious anomalies after IP parameters is considered, this can be observed in far field, near field and transient field; meanwhile, there is a clear relationship between the peak value of the amplitude anomaly ratio and phase anomaly difference before and after IP parameters is considered for the corresponding frequencies, as well as between the peak values and the resistivity, depth, and thickness of the layer which have IP response also; therefore, the IP information extracted from frequency domain electromagnetic sounding has a good outlook.