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VLF MEASUREMENTS: MODEL STUDIES AND BOREHOLE RESULTS

A.C.R. KETELAAR

ITC, International Institute for Aerial Surveys and Earth Sciences, Kanaalweg 3, 2628 EB Delft (The Netherlands)

Model experiments were made for the VLF method. Based on these mea- surements, an interpretation graph was designed which uses the real compo- nent only. With the help of this graph, an interpretation can be made to find depth and dip from a VLF field profile.

This interpretation has been checked against borehole results in explora- tion for vein-type sulphides.

An evaluation of the two shows that the depth information agrees, but that the dip information does not.

GROUNDWATER PROSPECTING WITH THE VLF METHOD - A CASE HISTORY IN PRECAMBRIAN BEDROCK

CONNY SVENSSON and SVEN FOLLIN

Engineering Geology, Department of Geotechnology, Institute of Technology, University of Lund, P.O. Box 725, S-220 07 Lund (Sweden)

The VLF method has been used to locate water-bearing fractures in the gneissic bedrock of Figelmara, Blekinge in southeastern Sweden. To ensure a correct interpretation of VLF anomalies complementary tests with other geophysical methods were carried out. Two VLF anomaly zones were veri- fied with drillings, only one of which proved to be water-bearing. The experi- ences from this case history definitely show that a VLF investigation always ought to be combined with a geological investigation.