Geophysical Journal | 2006 volume 28 4

Deep electromagnetic soundings with a fixed source of the field

© A.N. Kuznetsov

Features of using electromagnetic sounding arrays with a fixed source for horizontally inhomogeneous media based on physical data simulation are described. A considerable area of tens and hundreds km2 can be measured using this technology involving a source as a grounded electric circuit AB or a loop with the current Q. The most laborious part of the field work, repeated arrangement of the current circuit, is removed. This causes enhancing productivity of the work. At the same time, the use of two factors influencing the depth of investigation in one percent of soundings, the geometrical factor (value-and-azimuth-variable separation) and the time factor (variable frequency and time of recording) complicates the interpretation. In order to obtain unambiguous and reliable results, a priori data and a great volume of physical and mathematical modeling are needed. The nature of distribution of electromagnetic field of the grounded source within the horizontally inhomogeneous medium for frequency sounding and TEM sounding has been studied on a great number of models of local and regional heterogeneities. Much attention has been paid to the TEM sounding. The proposals concerning a rational technique of TEM sounding and involving the unification of the plane-tables of observations from different sources have been made. The techniques of improvement of the anomalies observed have been shown. Estimation of the favorable and unfavorable conditions of using this method has been carried out.

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