Abstract
A technique has been developed for accurate location of narrow vertical or inclined structures such as joints, fault planes, mineralized fissures, and weathered dykes. An alternating current of audio‐frequency is introduced conductively into the ground at a center‐point. Relative or absolute measurements of the tangential component of the resultant horizontal electromagnetic field are made at stations on concentric circles around the center‐point. Curves of the amplitudes, in decibels, are plotted as ordinates against the station positions. These are called the [Formula: see text]. The locations of peaks occurring vertically above current concentrations in narrow conducting zones are plotted on a map of the area and corresponding peaks are easily joined up to delineate such structures. Phase measurements have proved to be of minor importance for the location of geologic structures.
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