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Capacitive resistivity imaging with towed arrays


The capacitive resistivity (CR) technique is a generalization of the conventional DC resistivity method that facilitates measurements of electrical resistivity on engineered surfaces and highly resistive ground. The CR methodology allows the use of towed sensor arrays, thus enabling the rapid collection of high-resolution resistivity data. Under quasi-static conditions, CR data are equivalent to galvanic DC measurements so that CR datasets can be interpreted with conventional DC inversion algorithms. In this study, we demonstrate that the methodology and fundamental parameters of the CR technique facilitate spatial sampling at the centimeter scale for towing speeds of the order of 2.5 km/h. We argue that the dipole-dipole array is the most suitable geometry for dynamic CR measurements and present example data acquired with a prototype instrument using plate-wire combinations arranged in an equatorial geometry. The information content of raw CR data is found to be dominant over towing-induced noise and a direct comparison with DC profile data shows good agreement between both techniques. Based on these findings, we show that tomographic imaging is possible using datasets acquired with moving arrays. Closer investigation of the practical aspects of towed-array capacitive resistivity imaging (CRI) highlights the similarities with galvanic multi-electrode surveys, but the different geometric constraints and sampling regime of CRI give rise to advantages (high lateral resolution) as well as disadvantages (limitations in vertical resolution). We conclude our study with recommendations for practical CRI survey procedures and present a field example where we have successfully imaged a subsurface target in 3D. Towed-array CRI is found to provide equivalent (and in some ways superior) information about the shallow subsurface when compared to DC ERT (electrical resistivity tomography); it therefore widens the scope of electrical imaging surveys to environments where the conventional methodology would be impractical.

ISSN: 1083-1363
EISSN: 1943-2658
Serial Title: Journal of Environmental & Engineering Geophysics
Serial Volume: 12
Serial Issue: 3
Title: Capacitive resistivity imaging with towed arrays
Affiliation: British Geological Survey, Kingley Dunham Center, Keyworth, United Kingdom
Pages: 267-279
Published: 200709
Text Language: English
Publisher: Environmental and Engineering Geophysical Society, Englewood, CO, United States
References: 35
Accession Number: 2007-114300
Categories: Applied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch map
N52°30'00" - N53°00'00", W01°40'00" - W00°40'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Environmental & Engineering Geophysical Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200747
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