Study on application of comprehensive geophysical prospecting method in urban geological survey: taking hidden bedrock detection as an example in Dingcheng District, Changde City, Hunan Province

In order to ascertain the hidden bedrock and its spatial distribution in the urban low-resistance coverage area of a typical Huxiang basin in Hunan Province, a multi-method comprehensive experimental study is performed using the G4 geological survey profile in Dingcheng District, Changde City as an example. Firstly, the geological, stratigraphic, and structural characteristics of the study area are introduced. Secondly, based on the use of high-density resistivity method and controllable source audio magnetotelluric method for field exploration experiments, new methods and technologies such as wide-area electromagnetic method and micro-motion survey are introduced for comprehensive exploration experimental research. Finally, multiple detection methods are used to infer the vertical distribution of hidden Cambrian limestone, fault structures, and strata, and drilling verification is carried out at the target area, with good results. This survey study indicates that compared with traditional near-surface detection methods, the wide-area electromagnetic method has advantages that are unmatched by other methods such as high noise immunity and large detection depth. The method has obvious effect on the detection of the Cretaceous and Quaternary silty strata within 100 meters, and it is worthy of promotion.