Abstract: On 16 June 2022, high-frequency disturbances were observed in the three-orientation borehole apparent resistivity data in Tianshui. Their change pattern and amplitude were similar to those observed before the 20 April 2013 Lushan M_S 7.0, 22 July 2013 Minxian-Zhangxian M_S 6.6, and 8 August 2017 Jiuzhaigou M_S 7.0 earthquakes. Data collection and organization, anomaly investigation and analysis, and interference verification and treatment were conducted through a series of procedures, primarily including natural environment and site environment investigations, observational system verification, power frequency interference testing, identification of interference sources, line maintenance, and operational monitoring. It is found that Tianshui borehole apparent resistivity anomaly is not a pre-earthquake geophysical anomaly, but a high-frequency disturbance caused by the coupling of transformer grounding leakage current and the supply current during the instrumental measurement. This anomaly verification case provides a reference for power supply circuit planning, observation system maintenance and wire leakage anomaly investigation of borehole apparent resistivity stations.

Key words: apparent resistivity, high frequency disturbance, anomaly verification, leakage interference