Is It Time For The Next Generation Resistivity Inversion Programs?

The program RES2DINV and its variants have been widely used and have become the standard for electrical resistivity inversion software for nearly a whole generation of geophysicists, geologists, engineers and environmental technicians. It has been an extremely useful package, and for many geological environments it produces satisfactory depth results. However, there are many geological situations where the depth scale of the inverted (interpreted) section is quite exaggerated, giving the casual user the mistaken impression that detection depths are always a simple linear function of electrode spacing. This paper reviews the theory and points out some cases in which the depth of exploration is really much less than that implied by the vertical scale. It must be emphasized that the vertical scale of the output of this inversion program is always pseudo-depth, which does not equate to true depth in all situations. Suggestions are made for improving this shortcoming by compressing the model mesh upward by a factor proportional to the cumulative longitudinal conductance (S).