7. Geological Mapping Using VLF Radio Fields

McNeill, JN; Labson, Victor F.

doi:10.1190/1.9781560802686.ch7

Cited by 129 publications

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“…(McNeil and Labson 1992). Also at horizontal distance between 200 and 250 m, there is an observation of the filtered real and filtered imaginary both positively peaking together; this usually signifies a relatively thick overburden (McNeil and Labson 1992). This area is, therefore, marked T1.…”

Section: Resultsmentioning

confidence: 99%

“…Some instruments also measure the third magnetic component and/or the electric field. The electrical field is measured by inserting two probes in the ground spaced about 5 meters (McNeil and Labson 1992). VLF interpretation is generally qualitative or subjective in nature and sometimes may be subjected to quantitative interpretation with the aid of filtering technique from which the true filtered real are determined.…”

Section: The Vlf-em Surveymentioning

confidence: 99%

“…steeply dipping conductor or thickening conductive overburden). Some simple modeling may be carried out for simple geometric structures (McNeil and Labson 1992).…”

Section: The Vlf-em Surveymentioning

confidence: 99%

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Geophysical evaluation of groundwater potential in part of southwestern Basement Complex terrain of Nigeria

et al. 2017

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The geophysical assessment of groundwater in Awa-Ilaporu, near Ago Iwoye southwestern Nigeria was carried out with the aim of delineating probable areas of high groundwater potential. The area falls within the Crystalline Basement Complex of southwestern Nigeria which is predominantly underlain by banded gneiss, granite gneiss and pegmatite. The geophysical investigation involves the very low frequency electromagnetic (VLF-EM) and Vertical Electrical Sounding (VES) methods. The VLF-EM survey was at 10 m interval along eight traverses ranging between 290 and 700 m in length using ABEM WADI VLF-EM unit. The VLF-EM survey was used to delineate areas with conductive/fractured zones. Twenty-three VES surveys were carried out with the use of Campus Ohmega resistivity meter at different location and at locations areas delineated as high conductive areas by VLF-EM survey. The result of VLF-EM survey along its traverse was used in delineating high conductive/fractured zones, it is, however, in agreement with the delineation of the VES survey. The VES results showed 3-4 geoelectric layers inferred as sandy topsoil, sandy clay, clayey and fractured/fresh basement. The combination of these two methods, therefore, helped in resolving the prospecting location for the groundwater yield in the study area.

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Section: Resultsmentioning

confidence: 99%

Section: The Vlf-em Surveymentioning

confidence: 99%

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Geophysical evaluation of groundwater potential in part of southwestern Basement Complex terrain of Nigeria

et al. 2017

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“…Global scale signal strength contour maps for a number of important transmitters are given by McNeill and Labson (1991). The VLF bandwidth in the UK is usually dominated by the megawatt transmissions from Rugby (GBR=16 kHz, GBZ=19.6 kHz) and Anthorn (GQD=19 Hz).…”

Section: Introductionmentioning

confidence: 99%

Quantitative 2D VLF data interpretation

Beamish

2000

Journal of Applied Geophysics

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The ability of the VLF-R (Resistivity) method to provide quantitative subsurface resistivity information is examined. The frequencies used in conventional VLF (15 to 30 kHz) provide the deepest penetrations of the multi-frequency, extended method of RadioMT. Both methods are considered. VLF data, being effectively single frequency, are insufficient to resolve 1D (vertical) structure in any detail. At the site investigation scale, however, it is the departures from the background (vertically uniform) structure that are of interest. Improved methodologies for the quantitative assessment of VLF data derive from advances in regularised inversion techniques. Hydrogeological and waste-site examples of VLF-R survey data, aided by wide-band (VLF/RadioMT) synthetic modelling and inversion studies, are used to illustrate their shallow (0 to 20 m) resolution capabilities in conductive environments.

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“…The use of VLF radio fields in the general context of geological mapping has been extensively reviewed by McNeill and Labson (1991). The VLF technique makes use of one or more distant radio transmitters operating between 15 and 30 kHz.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional modelling of VLF data

Beamish

1998

Journal of Applied Geophysics

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The VLF technique is being increasingly applied to environmental and hydrogeological problems with a growing requirement for quantitative interpretation. One of the main difficulties with the VLF method stems from the directional polarisation of the transmitted field. To clarify VLF data interpretation when subsurface targets are complex and three dimensional, a modelling study was undertaken at VLF frequencies. A main concern is the interpretation of target strike directions when the transmitters used are rotated from principal-mode (i.e., two-dimensional) directions. Results for transmitter strike rotations of between 0 and 75° of the two principal modes are presented and discussed. For mapping purposes, the invariant apparent resistivity and phase provide important interpretational simplifications. For two-dimensional modelling/inversion, the field distortions introduced by directional complexity remain significant. The results also demonstrate the importance of apparent resistivity measurements in detecting and defining smallscale, isolated subsurface features.2

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7. Geological Mapping Using VLF Radio Fields

Cited by 129 publications

References 0 publications

Geophysical evaluation of groundwater potential in part of southwestern Basement Complex terrain of Nigeria

Geophysical evaluation of groundwater potential in part of southwestern Basement Complex terrain of Nigeria

Quantitative 2D VLF data interpretation

Three-dimensional modelling of VLF data

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