Secondary sources and linearization in geoelectric problems

Geoelectric problems include a base model (horizontally layered) and a base process (qual-stationary, pure electrodynamic). For any variable or distri buted source, solutions to these problems are expressed in terms of known i ntegrals. The base problem is well solved by computations and provides a ba se for interpretations. Any deviations from the base problem (e.g., increas e in dimensionsality) can be presented as the same base problem with an add itional (secondary) distributed source; in this case, the solution to the p roblem will be reduced to integral equations. This paper, however, demonstr ates that the above representation of the solution can give a number of ver y useful results, such as integral representation of derivatives by the par ameters of the base model, responses from some layers, approximate account of displacement currents, and fast calculation of the effect of multidimens ional disturbances of conductivity (Born linear approximation).