Verification of ERT Numerical Results of G11n and Traditional Configurations by Quasi Field Modelling

Summary Traditional geoelectric array configurations, such as e.g. the Wenner-Schlumberger or the Dipole-dipole, may be very effective in one-dimensional or robust two-dimensional investigations, but they are not sufficiently sensitive to SESEP inhomogeneities, which have a Small Effect on the Surface Electrical Potential distribution due to their small size and/or large depth or small resistivity contrast to the host. Their characterization is possible by applying quasi null arrays, which provide very small signals above a homogeneous half-space. Such arrays produced very good results in numerical investigations. In this paper their field applicability is demonstrated which has been heavily questioned. The quasi field analogue modelling experiments validated all of the numerical modelγling results. Many or all of the γ11n arrays could detect prisms and vertical sheets located at depths larger than those detectable by traditional geoelectric configurations. The horizontal resolution of the γ11n arrays, too, proved to be better than that of the traditional arrays. On the basis of this quasi field analogue study, γ11n arrays are expected to be well applicable to indicate SESEP targets (e.g., caves, mines, tunnels, tubes, cables, dykes, fractures), or to follow small variations in the subsurface conditions (monitoring of e.g. dams or waste deposits).