Location method of point interference source and its practical application in geoelectric field observation

China’s seismic network currently comprises 113 geoelectric field monitoring stations. To effectively utilize geoelectric field monitoring data for earthquake prediction, it is crucial to accurately differentiate between seismic and non-seismic anomalies. However, with the rapid development of China’s economy, agricultural production, and industrial construction around these monitoring stations, interference from electrical equipment leakage has escalated. This interference represents a significant non-seismic anomaly that adversely affects the quality of observation data and its application efficiency.　　1） The impact of electrical equipment leakage on geoelectric field observation can be characterized as follows: 　　2） The observation curve exhibits significant steps, peaks, or dips.　　3） The daily variation pattern of the geoelectric field is suppressed.　　4） The amplitude of each component of the geoelectric field varies due to the relative positions of the leakage points.　　5） The interference in each channel begins and ends at the same time, synchronized with the leakage period, although the degree of influence may differ.　　6） The interference amplitude is inversely proportional to the distance between the interference source and the electrode and directly proportional to the magnitude of the leakage current.　　Leakage interference within the measurement area constitutes a non-seismic anomaly that significantly impacts the quality of the observation data. Therefore, it is essential to identify and promptly investigate sources of interference in daily earthquake monitoring to minimize data loss caused by such interference. Currently, two types of interference sources can be identified based on examples encountered by stations: point source interference and dipole source interference. However, there is currently no high-precision positioning algorithm available for point sources.　　This study established a point source interference model based on a uniform semi-infinite space, analyzed the theoretical influence amplitude of point sources on geoelectric field observation through model theory, proposed a point source interference localization method, and applied the algorithm to the actual interference investigation work of Gaoyou Station in Jiangsu Province and Hanwang Station in Gansu Province.　　The position of the interference source was calculated based on the observed interference shape and change amplitude. The positioning direction and area were consistent with the actual interference source position. The positioning error of interference sources outside the measurement area was less than 2%, and the positioning error of interference sources inside the measurement area was less than 20 meters. 　　The main sources of positioning calculation errors are as follows: First, this method establishes a point source model based on a uniform semi-infinite medium, but the underground medium of the station is not completely uniform and isotropic. The non-uniform structure of the underground electrical properties will affect the propagation of electric field signals, resulting in certain calculation errors. However, this error has a relatively small effect, and the source of interference can still be located in a small area. Second, when the observation data is interfered with, the interference signal and the ground electric field observation signal are superimposed, and the ground electric field is constantly changing, making it difficult to accurately extract the interference amplitude. Inaccurate extraction of the interference amplitude leads to errors in the calculation results. In subsequent applications, multiple positioning calculations can be used to calculate the average and minimize the error in the calculation results. The positioning algorithm proposed in this article provides a sound solution for identifying point source leakage interference.