Geothermal Water Exploration of the Maoyanhe Hot Spring Scenic Spot in Zhangjiajie Using the Natural Electric Field Frequency Selection Method

Natural electric field frequency selection method was proposed by Chinese scholars in the 1980s on the basis of imitating the field observation method of the magnetotelluric method (MT). It can only measure the magnetotelluric field components of one or several frequencies on the surface to determine the existence of underground geological bodies. This method has played an important role in shallow groundwater exploration. This paper mainly discusses the application of frequency selection method in the exploration of underground hot water in the Maoyanhe Scenic spot, Zhangjiajie City, Hunan Province, in order to illustrate the effectiveness of the frequency selection method in water exploration. According to the situation of the construction site, nearly 20 geophysical prospecting survey lines of varying lengths were laid flexibly within the red line of the Maoyan River Scenic Spot. Firstly, three-frequency (170 Hz, 67 Hz and 25 Hz) measurements were carried out on each survey line to preliminarily determine the possible horizontal location of underground hot water. Secondly, in the vicinity of the low potential anomaly of the three-frequency curve, the fine measurement by using multi-frequency bipolar profile method was further carried out. The specific distribution of underground hot water was determined based on the principle of frequency domain sounding and the static effect characteristics of the electromagnetic method so as to provide a scientific basis for the drilling layout. Finally, the reliability of the frequency selection method is verified by two verification boreholes. The results indicate that the frequency selection method is one of the effective geophysical exploration methods in groundwater exploration.