Application of 3-D ERT for Enhanced Subsurface Imaging

In the geotechnical and environmental engineering, high resolution imaging technologies are required and 3-D ERT method is commonly used to obtain 3-D image of subsurface with quite high resolution, especially when the vertical structures such as fault or fractures are main target. In this paper, we show several examples of 3-D ERT imaging. The survey areas in the examples are (1) Granite quarry mine, (2) Abandoned lead-zinc mine, and (3) Test boreholes for fracture system evaluation. In the first example, by combining 3-D ERT with borehole radar reflection imaging, we could obtain 3-D attitude of fractures in a granite quarry to help the future mining plan. When the subsurface shows strong electrical anisotropy, we could obtain reasonable 3-D image of subsurface, which was used in safety analysis of subsurface. In the last example, by including the 3-D borehole deviations, we could obtain more accurate image of subsurface in the 2-D ERT case with the help of 3-D ERT program. These successful 3-D ERT results demonstrate that 3-D ERT is a very powerful method that can be used for wide application areas to obtain reliable 3-D earth images.