Electrical or direct current methods measure the bulk resistivity of subsurface materials to determine geologic structure and/or physical properties of the subsurface materials. An electrical current is introduced directly into the ground through an evenly spaced string of current electrodes. The resulting voltage potential difference is measured between a pair of potential electrodes. The current and the potential electrodes are generally arranged in a linear pattern. The apparent resistivity is the bulk average resistivity of all soils and rock influencing the flow of current.
The Electrical Resistivity method is useful for the following:
Substantial quantitative computer modeling is possible. The resulting models can provide accurate estimates of depths, thickness and electrical resistivities of subsurface layers. Surveys can be completed to depths of several hundred feet. Large distances can be covered in a relatively short period of time.
Resistivity surveys require a fairly large area far removed from power lines and grounded metallic structures. Profiling surveys can be more labor intensive than some other geophysical survey methods.