@article{eage:/content/journals/10.1111/j.1365-2478.1985.tb01362.x, author = "SCHULZ, R.", title = "INTERPRETATION AND DEPTH OF INVESTIGATION OF GRADIENT MEASUREMENTS IN DIRECT CURRENT GEOELECTRICS*", journal= "Geophysical Prospecting", year = "1985", volume = "33", number = "8", pages = "1240-1253", doi = "https://doi.org/10.1111/j.1365-2478.1985.tb01362.x", url = "https://www.earthdoc.org/content/journals/10.1111/j.1365-2478.1985.tb01362.x", publisher = "European Association of Geoscientists & Engineers", issn = "1365-2478", type = "Journal Article", abstract = "Abstract Gradient measurements in a homogeneous electrical primary field can easily be interpreted for simple models. The simplified solution (conducting or resistant body in a homogeneous space in a homogeneous electrical field) is often sufficiently accurate, as comparisons with the exact solution (body of finite resistivity in a homogeneous half‐space in a quasihomogeneous electrical field) show. The exact geometry of the body cannot be determined by gradient measurements; the same anomaly of apparent resistivity can be caused by different bodies. In particular, the similarity between a sphere and a cube of the same volume is very high. There is a distinct influence of the resistivity of the overburden: the higher this resistivity is, the stronger is the effect caused by a buried body. If a deviation of 10% of the apparent resistivity is assumed as the lower boundary at which a buried body can be detected by gradient measurements, the depth of investigation for a three‐dimensional body is approximately equal to its width; in the two‐dimensional case the thickness of the overburden can be twice the width. If the overburden has a resistivity which is higher than the resistivity of the substratum, these depths are greater. The greatest possible depth is approximately three times the width of the body.", }