Extract IP Effect From CSAMT

The Controlled Source Audio-frequency Magnetotellurics(CSAMT) is an important part of the geophysics.It is one kind of controllable source electromagnetic method which both in theory and applications have been successful.Effect of induced polarization(IP) is the charge accumulation in metal minerals and dectrolytes caused by the boundary surface,or the clay or the hole fettering ion movement caused.IP is a significant parameter,because it can be used to detect the economic valuable sulphide ore zone characteristics and geological structure.But trying to extract from the CSAMT effective IP information,on which the domestic and foreign scholars have also conducted certain research,until now did not have the explicit conclusion.This article first reviewed the development of extracting the IP information from the electromagnetic prospecting and summarized the domestic and foreign research present situation.Elaborated in detail the CSAMT method's basic theory, further discussed the forward problem of electromagnetic of the horizontal electrical dipole.Then has studied IP influence in the CSAMT,moreover model has simulated the CSAMT method's IP effect using Cole-Cole model on the polarizable earth.Has analyzed the electromagnetic field various components characteristic,and proposed that regarding extraction the IP information using the electric field y component the new development.Preliminary attempted to extract effective IP information.Finally, we theoretical calculated the apparent resistivity of dectromagnetic of the horizontal electrical dipole under the three-layer which the middle layer is polarized.Discussed the influence of IP on differ section of resistivity,we attempted to seek its change rule.It provides grounds for extracting IP information from CSAMT.Through the above-mentioned studies have shown that on the polarizable earth,IP effect influences H_y very small.E_y can well reflect IP effect.In layered earth,from the overall effect is concerned,the apparent resistivity of the electric field y-component definition response to IP effect better than others.As to differ section of resistivity, H section of resistivity help to find the existence of middle layer polarization.Apparent resistivity for the low resistance layer high-polarization response is better.As to Q section of resistivity,the middle layer polarization influence apparent resistivity very much little,it is difficult to reflect the IP information.