Magnetic Source Transient Electromagnetic Simulating Magnetotelluric 2D Inversion Method Technology Research

Magnetic source transient electromagnetic method for its unique advantages is widely used in mineral resource exploration and environmental engineering exploration and other fields. Since entering the new century, deep prospecting and engineering exploration require high precision and quantitative solving geological problems. But so far, there is no mature transient electromagnetic 2D and 3D inversion method which restricted the application of this method to a certain extent. The purpose of this paper is to study the magnetic source transient electromagnetic 2D inversion theory, considering the directly use of transient electromagnetic 2D and 3D forward to do optimization inversion is difficult, exploring another new way of transient electromagnetic 2D inversion, implementing its 2D inversion interpretation. In the paper, they have been studied mainly around the problems of magnetic source transient electromagnetic theory of 1D forward, the all-time apparent resistivity calculation of magnetic source transient electromagnetic, time-frequency conversion relations of magnetic source transient electromagnetic data and magnetotelluric data, magnetic source transient electromagnetic data simulating magnetotelluric 2D inversion.Based on magnetic source transient electromagnetic theory of 1D forward and the all-time apparent resistivity defined by vertical component of magnetic induction intensity, similarity has been theoretically studied by all-time apparent resistivity of transient electromagnetic and magnetotelluric Cagniard resistivity, selecting the best time-frequency conversion coefficient for the all-time apparent resistivity of transient electromagnetic and Cagniard resistivity time-frequency transformation. Then for a 1D and 3D theory model, simulating magnetotelluric 1D and 2D inversion have been proceed. 1D layered inversion results show that the relative errors of inversion resistivity and practical model resistivity are all less than 5.5%; the relative errors of inversion depth and practical model depth are all less than 5.5%, so the method can use to do magnetic source transient electromagnetic 1D inversion. For 3D model TEM response simulating magnetotelluric 2D inversion results show that TE and TM joint inversion results of the main section and side line and the actual low resistance body are in good agreement in both longitudinal and transverse and will not bring false anomaly which is better than TE mode and TM mode inversion results and out anomaly survey line inversion results; so at the top 3D abnormal body of the lines, using simulating magnetotelluric 2D TE and TM joint inversion method can accurately implement 2D inversion of 3D transient electromagnetic response.Finally simulating magnetotelluric 2D inversion for Shanxi a certain mining area magnetic source transient electromagnetic measurement data processing results show that the joint inversion result is superior to the inversion result of the TE mode and TM mode; according to the result of 15, 17 and 19 line joint inversion, combining with the mining rock electrical ore characteristics, ore-forming structure characteristics and scope of geochemical anomalies, it is concluded that the low resistivity anomalies in the inversion results may be related to mineralization which has obtained the good geological effect.A set of magnetic source transient electromagnetic field data processing procedure has been concluded based on simulating magnetotelluric 2D inversion method which will make the magnetic source transient electromagnetic data processing implement the 2D inversion interpretation by using simulating magnetotelluric 2D inversion method.