• Geophysics and Geophysical Exploration
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• v.11 no.4
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• pp.302-309
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• 2008

ERT imaging, especially 3-D method, is a very powerful means to obtain a very high resolution image of the subsurface for geotechnical or hydrogeological problems. In this paper, we introduce two examples of successful case histories, where the imaging targets were three-dimensional. First example is the case of 3-D fracture imaging for hydrogeologic application. In this example, the borehole deviation was a critical problem in the ERT imaging and we could obtain real 3-D attitude of fracture system by including the borehole deviation in the inversion. In the second case, we did field experiment to image the empty tunnel with the size of $2m{\times}2m$ and the target was very clearly imaged in 3-D space. In these examples, we could show that 3-D ERT imaging is a very powerful tool for the 3-D subsurface imaging and the method can provide enhanced imaging capabilities especially for the 3-D targets such as fractures and cavities or tunnel.