Electrical and electromagnetic methods in areas of complex geology

Abstract

In the application of electrical methods in areas of complex geology, two levels of complexity can be recognized. At lower levels of complexity, a fundamental dependence of resistivity on depth can be recognized. In such cases, the profile of resistivity with depth can be studied using various forms of sounding, in which array size, signal frequency, or a combination of both can be used. The complex subsurface structure can then be estimated by comparing a series of soundings. At higher levels of complexity, soundings are severely distorted by the complexity, and this approach is no longer useful. In such a case, it appears that the most effective approach is by observing electric or electromagnetic field behavior at many observation points over the surface of the earth. Examination of the spatial spectra of the field behavior then adds to the interpretability of the data, making interpretation possible.