Joint Inversion Of Apparent Resistivities And Impedance Phase From Magnetotelluric Sounding Data

In recent years, it requires more effective MT inversion methods in productive practice with the expansion of application area. Therefore, we must make further studies on inversion and imaging to provide more reliable and detailed geophysical foundation for geologic interpretation. The MT joint inversion is very important for reducing inversion ambiguity and Improve resolution. The method of joint inversion has been realized, and the sensitivity characteristics of phase and apparent resistivity have been discussed in this thesis. The effectiveness of joint inversion in reducing inversion ambiguity and static shift removing have been evaluated.(1) The sensitivity function of homogeneous half-space has been deduced and the characteristics of this sensitivity function under different situations have been analyzed. For 1-D model, the characteristics of the sensitivity function of phase and apparent resistivity have been discussed by analyzing Frechet derivative and slope of curve of the data from 1-D Modeling. And it has been proved that impedance phase has higher sensitivity than apparent resistivity under common situations.(2) The one-dimensional joint inversion of apparent resistivity and impedance phase from magnetotelluric sounding data has been realized in this thesis. The outcomes of apparent resistivity inversion, impedance phase inversion and joint inversion have been compared. Analysis of model test indicates that impedance phase inversion has a faster rate of convergence, apparent resistivity inversion is more stability, and the joint inversion has the advantage of convergence rate and stability. The outcome of joint inversion is more close to the real geoelectricity model.(3) The two-dimensional RRI joint inversion of apparent resistivity and impedance phase from MT data has been realized in this thesis. The benefits of apparent resistivity and impedance phase have been combined by the weight function in joint inversion, and the outcome of joint inversion is close to the real situation. The characteristic of horizontal and vertical resolution in different polarization-mode and the static shift in magnetotellunc sounding data have been discussed. The inversion test of theoretical model and the processing of actual data have proved that joint inversion, using apparent resistivity and impedance phase from magnetotellunc sounding, is very important for reducing inversion ambiguity and static shift removing.