A problem of non-uniqueness in the interpretation of electrical soundings, when identical trough- or peak-shaped apparent resistivity graphs for a three-layer case can be synthesized using different models for the middle layer. Identical peak-shaped graphs can be generated if the transverse resistance, Rt, remains a constant equal to hρ, where h is the thickness of the layer and ρ its true resistivity. Identical trough-shaped graphs can be generated if the longitudinal conductance, Gx, remains a constant equal to h/ρ. Such problems can be resolved if access is available to borehole geologic control and the range of h or ρ can be deduced.
Subjects: Earth Sciences and Geography.