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An evaluation of Bristow's method for the detection of subsurface cavities

Tony Lowry and Peter N. Shive
An evaluation of Bristow's method for the detection of subsurface cavities
Geophysics (May 1990) 55 (5): 514-520

Abstract

The Bristow method, an electrical resistivity technique employing a pole-dipole measurement array in conjunction with a simple graphical method of interpretation, has proven an effective means of locating subsurface cavities. There have been questions, however, regarding the limits of the method and whether the Bristow method is indeed the most suitable of the various electrical resistivity techniques for cavity detection. In hopes of resolving some of the controversy surrounding Bristow's method, resistivity traverses are numerically modeled over spherical and cylindrical cavities given a variety of circumstances. Using a slight variation of Bristow's original interpretive technique on modeled data, the size and location of subsurface cavities can be determined with surprising accuracy. However, when the simulation is altered to incorporate geologic noise, the maximum depth at which a cavity can be detected is found to be far less than has been reported in field investigations. In this instance the presence of a cylindrical cavity cannot be discerned beyond a depth to the top approximately equal to the diameter of the cavity, and spherical cavities are indistinguishable at depths much greater than the radius. One should note that the noise field generated for this model may not be representative of what would normally be found in the real earth. In the field, the maximum achievable depth of detection will vary depending on the actual geologic conditions and whether some technique is employed to reduce the effects of noise. In any case, a comparison of traverses using various electrode arrays confirms that the Bristow method is the most satisfactory of the applicable electrical resistivity techniques.


ISSN: 0016-8033
EISSN: 1942-2156
Coden: GPYSA7
Serial Title: Geophysics
Serial Volume: 55
Serial Issue: 5
Title: An evaluation of Bristow's method for the detection of subsurface cavities
Affiliation: Univ. Wyo., Dep. Geol. and Geophys., Laramie, WY, United States
Pages: 514-520
Published: 199005
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 17
Accession Number: 1990-031410
Categories: Engineering geologyApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 1990
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