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EXPLORATION GEOPHYSICS 



SURVEYS USING VERTICAL COIL ENERGIZING AND 

 RADIO FREQUENCIES 



A portion of a map of a typical electrical survey is illustrated in Figure 

 396, which shows data obtained in a survey conducted in Inyo County, 

 California. The high frequency "indications" in the plan view are tied-in 

 by the usual surveying methods to known property corners, bench marks, 

 and other features to allow later location of the indication should the 



Fig. 396. — Geoelectrical map, Inyo County, California. (I.R.E., Vol. 

 16, No. 10, Oct. 1928.) 



electrical survey stakes be removed. The approximate depth of the con- 

 ductor is obtained by plotting correction curves for traverses taken at 

 intervals along the indication, t By drawing a curve through the indicated 

 depths at each of these traverses, the indicated electrical axis of the con- 

 ductor is located. The correction curves for each traverse are shown in 

 the figure. The curves shown are drawn by imagining the traverses 

 as being rotated 90 degrees to allow the curves to be plotted in the plane 

 of the paper. The reversal of the index curves at the fault and the dis- 

 placement of the conductor are very noticeable. 



An interesting example of the continuity of a mineraHzed zone may be 



t J- J- Jakosky, loc. cit. 



