Abstract
Abstract The telluric field frequency selection method (TFFSM) has been proposed for more than 40 years and has achieved good exploration results in groundwater exploration. The cause of its anomaly formation has always been one of the issues that people are concerned about. This article mainly explains the causes of TFFSM anomalies through experimental detection near a known water well, and demonstrates its relevant issues in application. Firstly, the triple-frequency observation was carried out along the survey line to quickly determine the location of groundwater. Secondly, the synchronous observations of three type of frequency selectors in the case of electrode separation and electrode sharing were adopted respectively. Thirdly, the variation of TFFSM exploration results with electrode spacing (MN) was studied. Finally, audio-magnetotelluric method (AMT) measurements were taken at two points on the survey line. Through the above experiments, we obtained the potential difference (ΔV) profile curves and their pseudo-sections of TFFSM under different conditions, as well as the power spectral density curves of electric and magnetic field of AMT, and corresponding apparent resistivity curves. According to the analysis of the experimental results, it can be concluded that the existence of groundwater will cause static effects in the detection results of TFFSM. TFFSM has relatively loosen grounding requirements for electrodes, but the size of MN has a certain influence on exploration depth. From the comparison between TFFSM and AMT, the former has stronger anti-interference ability and site adaptability, and TFFSM can be applied to urban geological exploration in the future.