Application of comprehensive geophysical prospecting method in detecting concealed karst collapses
ZHANG Jian1(), FENG Xu-Liang2(), YUE Xiang-Ping3
1. The First Geological Mineral Exploration Institute of Gansu Provincial Geology and Mineral Bureau, Tianshui 741020,China 2. School of Earth Sciences and Engineering,Xi’an Shiyou University,Xi’an 710065,China 3. Xi’an Northwest Nonferrous Geophysical and Geochemical Exploration Co., Ltd., Xi’an 710068, China
Karst is widely distributed in China. However, geological disasters frequently occur in karst zones due to the fragile geological environment, which seriously threatens the safety of people’s life and property and cause huge economic losses. In this study, the controlled source audio-frequency magnetotelluric (CSAMT) method and microgravity were used to extract residual gravity anomalies through the two-dimensional inversion of pseudosections and multi-scale wavelet analysis. As a result, rock-soil interfaces of karst zones and the development zones of strong karst were well divided; the locations, burial depths, scales, and spatial distribution of karst caves were delineated. As verified by drilling, the rock-soil interfaces and strong-karst development zones determined by CSAMT interpretation were roughly consistent with those revealed by boreholes, and the sizes and burial depths of collapsed karst caves that were delineated by microgravity roughly correspond to those revealed by boreholes of engineering exploration. These results show that the CSAMT combined with the microgravity method can achieve significant effects in the detection of concealed karst collapses and serves as a scientific detection method for the early warning of the prevention and treatment of potential karst collapses and similar geological disasters.
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