Research Of The Two-dimensional Magnetotelluric Inversion With Induced Polarization Effect

The MT method is an effective means of geophysical exploration. It is widely used in manydomain of today’s geophysical exploration, such as the oil and gas exploration and study of thedeep crust structure. Two-dimensional inversion of magnetotelluric method technology is nowmore mature, such as Fast Relaxation Method (RRI), Conjugate gradient method (CGG), Occamand others. Most of the existing two-dimensional inversion algorithms only consider theelectromagnetic effects of the underground media, while ignoring the effect of inducedpolarization (IP). Magnetotelluric inversion study is relatively small considering the effect ofinduced polarization. In order to expand areas of application of the magnetotelluric method,improving the effect of the application, two-dimensional magnetotelluric inversion study toconsider the effect of induced polarization is important. Since the1970s, domestic scholars beganto study induced polarization information in the natural field source electromagnetic signalextraction. In this paper, Cole-Cole model was introduced into the Helmholtz equation,considering the effect of induced polarization and electromagnetic effects in inversion in order toexplore the feasibility of extraction of the Cole-Cole model parameters.In this paper non-uniform grid limit element method is used to forward computation. TheJacobian is Calculated in finite elements using reciprocity. At last obtain the Jacobian matrix withcomposite function derivative rule. After getting the partial derivative matrix, building the matrixequation and solving it. Occam method is not only fitting the measured data, but also smoothingthe model on horizontally and vertically and it has good stability. Because of the Jacobian matrixof different physical parameters are quite different in the value, and this difference is graduallybeing enlarged with the calculations. Therefore, we weighted matrix to obtain the behavioroptimization. In view of the characteristics of the Cole-Cole model, the parameter range is limited.From the trial inversion with the synthetic and real data, the validity and practicability of thisinversion algorithm is verified.