Journal Article10.1111/J.1365-2478.1983.TB01085.X
Linear filtering of VLF dip-angle measurements
M. Karous,S.E. Hjelt +1 more
282
TL;DR: In this paper, the authors proposed an interpretation technique based on discrete linear filtering of VLF data, where the output of the described filtering results is expressed in terms of an equivalent current density at a specified depth that would cause the measured magnetic field.
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Abstract: The suggested interpretation technique is based on discrete linear filtering of VLF data. The output of the described filtering results is expressed in terms of an equivalent current density at a specified depth that would cause the measured magnetic field. The most practical six-point filter gives an accuracy of 8%. The filter is an extension of the commonly used Fraser filter to process VLF dip-angle data. Filtering the same data set for various depths gives an idea about the change of current density with depth. Areas with high current-density correspond to good conductors. The conductor dip can also be determined. The use of the technique is illustrated on theoretical and field examples. In all cases a good correlation with original models and other types of geophysical measurements was obtained. As shown in the last example, the filtering technique is also applicable in interpretation of other electromagnetic methods.
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Citations
In-Phase/Quadrature Signatures of a Very LowFrequency Electromagnetic Survey for the Delineation of Cassiterite at Rafin Bareda, DutsenWai, Kaduna State, Nigeria
M. Adamu,Nasir K Abdullahi,M. Dogara +2 more
TL;DR: VLF-EM technique was used to delineate cassiterite zones at Rafin Bareda, DutsenWai, Kaduna State, Nigeria. The technique revealed continuous and extending mineralized zones of cassiterite on profiles G and H.
VLF-EM and VES: an application to groundwater exploration in a Precambrian basement terrain SW Nigeria
TL;DR: In this paper, a total of 2100 VLF-EM data plus selected selected VES points were covered over 7 traverses with length varying from 3000 to 4500 m. Results of the investigation indicate that a HKH sounding curve is obtained with a maximum of five subsurface layers comprising: the top soil, clay/sandy clay unit, the fresh basement, fractured basement and the basement bedrock.
The role of geophysics in the investigation of waste disposal site in ikare-akoko area, southwestern nigeria
Omowumi Oluwafemi
- 28 Nov 2012
TL;DR: In this article, the impact of solid waste disposal at Alapata area along Secretariat Road, Ikare Akoko on the quality of the surrounding surface and groundwater sources was investigated.
Noise reduction and data recovery for a VLF-EM survey using a nonlinear decomposition method
TL;DR: In this paper, the authors used a nonlinear decomposition technique called the empirical mode decomposition EMD method with the Hilbert transform to obtain more reliable low frequency electromagneticVLF-EM data.
The Geophysical Investigation of Leachate Formation in Mgbuka Obosi, Idemili North Local Government Area of Anambra State, Nigeria
TL;DR: The geophysical investigation of leachate formation at Mkpuka Obosi Dumpsite reveals the presence and spatial distribution of leachate plumes, highlighting the need for improved landfill management practices.
References
Measurement and Analysis of Random Data
TL;DR: This book is concerned with the general problems of measuring, analysing and interpreting random data and also with the planning of experiments and is not biased toward any one field of application.
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Contouring of vlf‐em data
TL;DR: A data manipulation procedure is described which transforms noisy noncontourable data into less noisy contourableData, thereby eliminating the dynamic range problem and reducing the noise problem.
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Computation of type curves for electromagnetic depth sounding with a horizontal transmitting coil by means of a digital linear filter
TL;DR: In this article, a linear relationship between the mutual coupling ratio and the kernel function in the integral expression for it is described, which can be determined by first computing sample values of the kernel functions and then subjecting these to a digital linear filter.
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Numerical VLF modeling
TL;DR: In this article, the VLF response of laterally inhomogeneous and anisotropic models is calculated numerically using the finite element method, and the direction of the dip can be determined from the anomaly profiles of all diagnostic parameters.
51
A note on the linear filter method of computing electromagnetic sounding curves
R. K. Verma,O. Koefoed +1 more
TL;DR: In this paper, the values of the filter coefficients used for the computation of electromagnetic sounding curves are studied in conjunction with the value of the input function to the filter, or the range of values which the input functions may assume, and the filters are broken off at such a place that the error in the sum of the products of filter coefficient and input function does not exceed a prescribed value.
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