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Application of geoelectrical resistivity imaging and VLF-EM for subsurface characterization in a sedimentary terrain, south-western Nigeria

Aizebeokhai, A. P. and Oyeyemi , Kehinde D. (2015) Application of geoelectrical resistivity imaging and VLF-EM for subsurface characterization in a sedimentary terrain, south-western Nigeria. Arabian Journal of Geoscience, 8 (6). pp. 4083-4099.

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Geoelectrical resistivity imaging and very-low frequency electromagnetic (VLF-EM) geophysical techniques were integrated to characterize the subsurface as part of preliminary investigations for groundwater resource assessment, development and management in a sedimentary terrain, southwestern Nigeria. Six parallel 2D geoelectrical resistivity field data were collected using Wenner array. VLF-EM data were equally collected along the same 2D geoelectrical resistivity traverses. Also, four vertical electrical soundings (VES) were conducted on the site using Schlumberger array to provide layering information. The plots of filtered in-phase and quadrature components of the VLF-EM data as well as their corresponding Fraser and Karous-Hjelt pseudo-sections discriminate between the conductive and resistive subsurface features. The observed apparent resistivity data for the 2D traverses were inverted to produce 2D inverse model resistivity images and then collated to 3D data set which was inverted to produce 3D inverse model resistivity images of the subsurface. Isoresistivity surfaces for 750 , 1000 and 1500 extracted from the 3D inverse model shows the 3D distribution of these resistivities in the study site. High resistivity layer at depth range of 10.2 – 16.4 m and thickness ranging from 11.0 – 21.0, which overly the aquifer unit, delineated in the VES and 2D /3D geoelectrical resistivity imaging could not be distinctly discriminated in the Fraser and Karous-Hjelt pseudo-sections of the VLF-EM data. Some fractures or joints which are thought to serve as the main conduit path for groundwater recharge are clearly revealed in Fraser and Karous-Hjelt pseudosections. Thus, the use of geoelectrical resistivity or VLF-EM technique alone is inadequate to characterize the subsurface features in the study site; consequently, the integration of 2D and 3D resistivity imaging with VLF-EM technique enhanced the degree of reliability of the subsurface characterization in the study site.

Item Type: Article
Subjects: Q Science > Q Science (General)
Q Science > QE Geology
Divisions: Faculty of Engineering, Science and Mathematics > School of Physics
Depositing User: Mr. K. D. Oyeyemi
Date Deposited: 25 Feb 2016 07:28
Last Modified: 26 Feb 2016 09:58

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