A two-dimensional forward and backward algorithm for the controlled-source audio-frequency magnetotelluric （CSAMT） method is developed to invert data in the entire region （near, transition, and far） and deal with ...A two-dimensional forward and backward algorithm for the controlled-source audio-frequency magnetotelluric （CSAMT） method is developed to invert data in the entire region （near, transition, and far） and deal with the effects of artificial sources. First, a regularization factor is introduced in the 2D magnetic inversion, and the magnetic susceptibility is updated in logarithmic form so that the inversion magnetic susceptibility is always positive. Second, the joint inversion of the CSAMT and magnetic methods is completed with the introduction of the cross gradient. By searching for the weight of the cross-gradient term in the objective function, the mutual influence between two different physical properties at different locations are avoided. Model tests show that the joint inversion based on cross-gradient theory offers better results than the single-method inversion. The 2D forward and inverse algorithm for CSAMT with source can effectively deal with artificial sources and ensures the reliability of the final joint inversion algorithm.展开更多
The cross-gradients joint inversion technique has been applied to multiple geophysical data with a significant improvement on compatibility, but its numerical implementation for practical use is rarely discussed in th...The cross-gradients joint inversion technique has been applied to multiple geophysical data with a significant improvement on compatibility, but its numerical implementation for practical use is rarely discussed in the literature. We present a MATLAB-based three-dimensional cross-gradients joint inversion program with application to gravity and magnetic data. The input and output information was examined with care to create a rational, independent design of a graphical user interface (GUI) and computing kernel. For 3D visualization and data file operations, UBC-GIF tools are invoked using a series of I/O functions. Some key issues regarding the iterative joint inversion algorithm are also discussed: for instance, the forward difference of cross gradients, and matrix pseudo inverse computation. A synthetic example is employed to illustrate the whole process. Joint and separate inversions can be performed flexibly by switching the inversion mode. The resulting density model and susceptibility model demonstrate the correctness of the proposed program.展开更多
In order to effectively solve the low precision problem of the single gravity density inversion and the magnetic susceptibility inversion,and the limitation of the gravity?magnetic joint inversion method based on the ...In order to effectively solve the low precision problem of the single gravity density inversion and the magnetic susceptibility inversion,and the limitation of the gravity?magnetic joint inversion method based on the petrophysical parameter constraint,this paper studies the three-dimensional gravity?magnetic cross-gradient joint inversion based on the structural coupling and the fast optimization algorithm.Based on the forward and inversion modeling of three-dimensional gravity density and three-dimensional magnetic susceptibility using the same underground grid,along with cross-gradient coupling as the structural cons train t,we propose a new gravit y?magnetic joint inversion objective function including the data fitting term,the total variation regularization constraint term and the crossgradient term induced by the structural coupling?The depth weighted constraint and the data weighting constraint are included into the objective function,which requires different physical property models to minimize their respective data residuals.At the same time,the cross-gradient term tends to zero,so that the structure of the gravity and magne ic models tends to be consistent.In realization,we address a fast and efficient gradient algorithm to iteratively solve the objective function.We apply this new joint inversion algorithm to the 3D gravity-magnetic model inversion test and compare it with the results of a single inversion algorithm.The experimental tests of synthetic data indicate that the gravity-magnetic cross-gradient joint inversion method can effectively improve the accuracy of the anomaly position and numerical accuracy of the inverted anomaly physical parameters compared with the single physical inversion method.展开更多
基金jointly sponsored by the Fundamental Research Funds for the Central Universitiesthe National Natural Science Foundation of China(No.41374078)
文摘A two-dimensional forward and backward algorithm for the controlled-source audio-frequency magnetotelluric （CSAMT） method is developed to invert data in the entire region （near, transition, and far） and deal with the effects of artificial sources. First, a regularization factor is introduced in the 2D magnetic inversion, and the magnetic susceptibility is updated in logarithmic form so that the inversion magnetic susceptibility is always positive. Second, the joint inversion of the CSAMT and magnetic methods is completed with the introduction of the cross gradient. By searching for the weight of the cross-gradient term in the objective function, the mutual influence between two different physical properties at different locations are avoided. Model tests show that the joint inversion based on cross-gradient theory offers better results than the single-method inversion. The 2D forward and inverse algorithm for CSAMT with source can effectively deal with artificial sources and ensures the reliability of the final joint inversion algorithm.
文摘The cross-gradients joint inversion technique has been applied to multiple geophysical data with a significant improvement on compatibility, but its numerical implementation for practical use is rarely discussed in the literature. We present a MATLAB-based three-dimensional cross-gradients joint inversion program with application to gravity and magnetic data. The input and output information was examined with care to create a rational, independent design of a graphical user interface (GUI) and computing kernel. For 3D visualization and data file operations, UBC-GIF tools are invoked using a series of I/O functions. Some key issues regarding the iterative joint inversion algorithm are also discussed: for instance, the forward difference of cross gradients, and matrix pseudo inverse computation. A synthetic example is employed to illustrate the whole process. Joint and separate inversions can be performed flexibly by switching the inversion mode. The resulting density model and susceptibility model demonstrate the correctness of the proposed program.
基金We would like to thank reviewers very much for their valuable comments and suggestions.The research is supported by National Key R&D Program of the Minis try of Science and Technology of China with the Project“Integration Platform Construction for Joint Inversion and Interpretation of Integrated Geophysics(Grant No.2018YFC0603500)”National Natural Science Foundation of China under grant number 91630202.
文摘In order to effectively solve the low precision problem of the single gravity density inversion and the magnetic susceptibility inversion,and the limitation of the gravity?magnetic joint inversion method based on the petrophysical parameter constraint,this paper studies the three-dimensional gravity?magnetic cross-gradient joint inversion based on the structural coupling and the fast optimization algorithm.Based on the forward and inversion modeling of three-dimensional gravity density and three-dimensional magnetic susceptibility using the same underground grid,along with cross-gradient coupling as the structural cons train t,we propose a new gravit y?magnetic joint inversion objective function including the data fitting term,the total variation regularization constraint term and the crossgradient term induced by the structural coupling?The depth weighted constraint and the data weighting constraint are included into the objective function,which requires different physical property models to minimize their respective data residuals.At the same time,the cross-gradient term tends to zero,so that the structure of the gravity and magne ic models tends to be consistent.In realization,we address a fast and efficient gradient algorithm to iteratively solve the objective function.We apply this new joint inversion algorithm to the 3D gravity-magnetic model inversion test and compare it with the results of a single inversion algorithm.The experimental tests of synthetic data indicate that the gravity-magnetic cross-gradient joint inversion method can effectively improve the accuracy of the anomaly position and numerical accuracy of the inverted anomaly physical parameters compared with the single physical inversion method.
