Rock fracture compliance derived from time delays of elastic waves

ABSTRACT The purpose of this study is to compare the reliability of various methods of estimating normal rock fracture compliance from elastic wave measurements. We compare ultrasonic through‐transmission laboratory measurements for a smooth fracture in a Westerly granite specimen with numerical sim...

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Bibliographic Details
Published in:Geophysical Prospecting 2010-11, Vol.58 (6), p.1111-1122
Main Authors: Möllhoff, M., Bean, C.J., Meredith, P.G.
Format: Article
Language:English
Subjects:
Applied geophysics
Compliance
Computer simulation
Delay
Earth sciences
Earth, ocean, space
Elastic waves
Estimates
Exact sciences and technology
Fracture
Fracture mechanics
Group delay
Internal geophysics
Mathematical models
Rock
Time delay
Transmission coefficient
Ultrasonic
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Summary:ABSTRACT The purpose of this study is to compare the reliability of various methods of estimating normal rock fracture compliance from elastic wave measurements. We compare ultrasonic through‐transmission laboratory measurements for a smooth fracture in a Westerly granite specimen with numerical simulations and analytical solutions. The focus is on deriving compliance from time delays. The influence of specimen and source transducer width was constrained using numerical wave simulations. We find that measured ultrasonic phase delays are better suited to estimate the fracture compliance than group delays. Using the frequency domain instead of the time domain increases the accuracy of the fracture compliance estimates. We further show that for cases where precise phase delay measurements are unavailable, employing first break times in conjunction with numerical simulations can be considered as an alternative.
ISSN:0016-8025
1365-2478
DOI:10.1111/j.1365-2478.2010.00887.x