The Regularization Joint Inversion For Direct Current Resistivity And Audio Magnetotelluric Method

Shallow surface is the main space for human survival and civilization development,and also the main place for human engineering construction and resource exploitation.But it is also the main area of waste discharge and waste disposal.However,it still plague human for the present construction and production life by the a variety of unknown situations and various geological disasters in the underground area.The DC resistivity method(DC)and the audio magnetotelluric method(AMT)are two main methods to explore the underground space in the shallow region,which are widely used in engineering construction and resource exploration.However,because of the constraints of the power supply current and distribution device space by DC resistivity,which makes the method very obvious for the near surface electricity,but received less deep information.At the same time,the audio magnetotelluric method has the characteristics of large penetration depth and sensitive to low resistance,but it is easily affected by the shallow electric inhomogeneity and produces false anomalies.Based on the objective needs of social development for shallow surface geophysics,and combined with the advantages and disadvantages for the audiomagnetotelluric and DC resistivity method in the near surface geophysical exploration.So in this paper,regularization theory is used as the basis of inversion,research the joint inversion of one-dimensional and two-dimensional combination for DC resistivity and audio magnetotelluric data.The main research work from the following three aspects:(1)From the theorys of regularization inversion,Focuses analysis the theory of regularized objective function of the parts,the composition of data error function,the selection of regularization factor,etc.And a method of adaptive selection for regularization factor is proposed.Analysis the calculation results of inversion for stability factor of different inversion characteristics at with or without a priori model.Combined with the nonlinear conjugate gradient method based on the strong Wolfe line search step,the fast solution of the regularized objective function is achieved.(2)Based on the in-depth research for the regularization inversion theory,from the forward of DC resistivity and audio magnetotellurics on one-dimensional.In this paper,the algorithm of data error function and partial derivative matrix based on different types of data is discussed in detail.Combined with the horizontal layered model,the effect of regularized joint inversion under different stability factors is discussed.(3)The forward modeling of the two dimensional DC resistivity method and the audio magnetotelluric method is based on the shrinkage mesh finite element method.Based onthe analysis of the variational form of the two methods,Summed up the commonly used several major integral form in the unit grid coefficient matrix.And the LDLT decomposition algorithm is used to solve the large sparse linear system;The fast calculation of sensitivity matrix in joint inversion is achieved by the exchange theorem.At last,the inversion ability of the joint inversion model is analyzed and compared by the simple and complex model,the effectiveness of the joint inversion method is verifed.