To address the computational complexity and cumbersome matrix assembly inherent in the Space-Wavenumber Mixed-Domain Method based on the Finite-Element Method (SWMDM-FEM) for three-dimensional (3D) Direct Current (DC) resistivity simulations, we propose an enhanced numerical approach. This approach utilizes two-dimensional (2D) Fourier transform technology to convert the 3D resistivity problem into a one-dimensional (1D) problem within the space-wavenumber mixed domain, which is then solved using the finite-difference method (FDM). By integrating the efficiency of Fourier transform with the simplicity of FDM, this method significantly enhances the efficiency of 3D numerical simulations in DC-resistivity methods. The accuracy of our algorithm is first validated using a spherical anomalous model, followed by testing with a model combining a low-resistivity cuboid and a high-resistivity sphere, demonstrating the method’s superior computational efficiency over the SWMDM-FEM. Subsequently, the proposed algorithm in this paper was tested using a cubic anomaly model. The number of iterations of the algorithm required to achieve the preset convergence accuracy was focused on and counted under different resistivity differences between the anomalous body and the background medium, different total grid numbers in the computational region, and different burial depths of the anomalous body so as to verify that the proposed algorithm has good convergence performance. At the same time, the test results show that under the premise of meeting the preset accuracy requirements, the number of iterations when the algorithm converges is only related to the resistivity difference between the anomalous body and the background medium, and has no correlation with the total number of grid divisions and the burial depth of the anomalous body. Finally, the E-SCAN method was used to carry out three-dimensional observation on the composite model, and the electromagnetic response characteristics of the anomalies were systematically analyzed. It is found that the position of the power supply point significantly impacts the observational outcomes. The E-SCAN method shows higher resolution in terms of identifying low-resistivity bodies but has limited capability in recognizing high-resistivity bodies. These findings provide a strategic workflow for practical geophysical exploration: rapid anomaly delineation using the E-SCAN method followed by high-precision 3D inversion.
Ling et al. (Wed,) studied this question.