Geophysical characteristics and geological interpretation of karst strata

To investigate the karst development characteristics in a water conservancy project area in Yunnan Province, a geophysical survey using transient electromagnetic and microtremor detection methods has been conducted. Analysis of the survey data shows that karstification can cause inhomogeneity of the physical properties in carbonate strata; the karst development in the engineering area is significantly affected by the structural plane and lithology distribution of the rock and it shows a certain layering in the vertical direction. The strong weathering zone and the fracture zone is often accompanied by the development of karst with the presence of large scale or discrete low resistivity and low wave velocity anomalies. Erosion along fractures can change the electrical parameters of the rock to a very large extent, but the impact on its elastic parameters is relatively low. The discrete coefficients of electrical and elastic parameters of rock can be used to characterize the resistance to erosion and weathering of rock mass as well as the degree of karst development. In combination with the magnitude and distribution of physical properties of rock, these coefficients can effectively help to analyze the karst development and nature of its filling material.