新しい地下電気探査における逆解析過程とその評価

Abstract

New electrical prospecting techniques utilizing effective surface and subsurface solid electrode arrays, large continuous data processing, high density computer simulation and visualization have become important useful exploration tools increasingly for detecting deeply located mineral or low mineralized deposit, energy and groundwater reservoirs, geological fracture zones and rock interior structures, and also for monitoring groundwater in rock mass and contermination, nuclear waste repository and various changes of underground structures.An important objective of electrical methods including resistivity tomography techniques, is to maximize, extract and enhance the response due to target inhomogeneities using surface electrodes on the various ground conditions and buried electrodes in boreholes, tunnels and other underground conditions. Recently, new computerized resistivity section construction techniques has been mainly developed with emphasis on improvement of the reliability to extract the subsurface informations for the domains of groundwater and environmental explorations. For an example, a future work in improving the reliability is to design effective surface and solid electrode array combinations under the restricted field conditions by new prediction and feedback techniques.This paper begins with a review of the recent activities about development of elements as an aid to new surface and subsurface electrode array techniques. Next, the basic concepts of resistivity array methods including high accuracy forward modeling, high resolution inversion, sensitivity distribution and image reconstruction from computerized tomography procedure, are reviewed. And also, some results on the improvement of reliability of electrical methods have been discussed by using the examples of subsurface signal extraction and enhancement, investigated by the authors.