Application of Prior-Information-Constrained Audio-Magnetotelluric Method in Rock Salt Deposit Exploration

The study area is located within a fault-controlled sedimentary basin and hosts abundant evaporite resources, including gypsum and rock salt, indicating favorable prospects for exploration and development. Previous investigations of rock salt deposits in this area have primarily relied on drilling and seismic exploration. Although these methods provide high resolution, they are associated with high costs and significant environmental disturbance, which to some extent constrain efficient resource development. To investigate the three-dimensional electrical characteristics of the rock salt deposit, six audio-frequency magnetotelluric (AMT) survey lines were deployed in the study area, and a total of 42 MT stations were acquired. Dimensionality analysis indicates that the subsurface geological structure exhibits pronounced three-dimensional electrical features. Subsequently, a prior-information-constrained three-dimensional inversion was conducted, leading to the establishment of a resistivity structural model characterized by “shallow low resistivity–intermediate high resistivity–deep low resistivity” zoning. Integration with regional geological data suggests that the shallow low-resistivity layer corresponds to Quaternary and Neogene unconsolidated sediments, whereas the deep low-resistivity zone is interpreted as the potential occurrence zone of rock salt deposits. The results demonstrate that three-dimensional AMT exploration provides reliable geophysical evidence for deep mineral prospecting and offers technical support for the scientific evaluation of salt resources and the development of underground gas storage caverns.