Numerical simulation for the influence of two-end grounded cables on georesistivity observation

Two-end grounded cables often generate interference to continuous georesistivity observation at fixed sites for earthquake monitoring and prediction in China. By taking the grounded cables as two-end grounded resistors and simplifying the medium of geoelectric observation sites into horizontally inhomogeneous three-layered medium, a coupled physical model is built up in this paper. Based on this model, influences of two-end grounded cables on georesistivity observation are simulated under different electric structures by using the finite element analysis software ANSYS. Furthermore, the effects of interference factors, such as position, azimuth and buried depth of electrodes, on georesistivity observation are analyzed. And the interference mechanisms are also discussed. Besides, some existing interferences are also presented to give out a comparative study. The results showed that the first, the grounded cables can cause local adjustment of the symmetric underground electric field distribution generated by the current electrode, affecting normal georesistivity observation; the second, the effects of grounded cables on georesistivity observation, mainly depend on position of cables and their azimuth; the third, the effects tend to be reduced obviously with buried depth of electrodes increasing; and the forth, the difference of the electric structures determine the magnitude of interference. The simulation results are of significance as a reference to analyzing the similar resistivity anomalies, choosing the evaded distance of the interference source and the reform of the observing system.