Numerical modeling of the 2D time-domain transient electromagnetic secondary field of the line source of the current excitation
Liu Yun1, Wang Xu-Ben2, and Wang Yun1
1. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry Chinese Academy of Sciences, Gui Yang 550002, China.
2. School of Geophysics, Chengdu University of Technology, Chengdu 610059, China.
Abstract：
To effectively minimize the electromagnetic field response in the total field solution, we propose a numerical modeling method for the two-dimensional (2D) time-domain transient electromagnetic secondary field of the line source based on the DuFort-Frankel finite-difference method. In the proposed method, we included the treatment of the earth-air boundary conductivity, calculated the normalized partial derivative of the induced electromotive force (Emf), and determined the forward time step. By extending upward the earth–air interface to the air grid nodes and the zero-value boundary conditions, not only we have a method that is more efficient but also simpler than the total field solution. We computed and analyzed the homogeneous half-space model and the flat layered model with high precision—the maximum relative error is less than 0.01% between our method and the analytical method—and the solution speed is roughly three times faster than the total-field solution. Lastly, we used the model of a thin body embedded in a homogeneous half-space at different delay times to depict the downward and upward spreading characteristics of the induced eddy current, and the physical interaction processes between the electromagnetic field and the underground low-resistivity body.
LIU Yun,WANG Xu-Ben,WANG Bin. Numerical modeling of the 2D time-domain transient electromagnetic secondary field of the line source of the current excitation[J]. APPLIED GEOPHYSICS, 2013, 10(2): 134-144.
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2013, Vol. 10 
