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Effects of shock-induced cracks on the ultrasonic velocity and attenuation in granite

Ai, Huirong A. and Ahrens, Thomas J. (2007) Effects of shock-induced cracks on the ultrasonic velocity and attenuation in granite. Journal of Geophysical Research B, 112 (B1). Art. No. B01201. ISSN 0148-0227. doi:10.1029/2006JB004353.

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Measurements of the compressional wave velocity and the attenuation coefficients of 1-cm cubes were conducted. Samples were taken at various radii and depths beneath a 20 × 20 × 15 cm San Marcos granite block, impacted by a lead bullet at a velocity of 1200 m/s. The damage parameters of the cubes are calculated from the measured preimpact and postimpact P wave velocities, V_(p0) and V_p, and the crack density is inverted from the measured P wave velocities. The anisotropic orientation of cracks is more obvious from the attenuation than crack density and damage parameters calculated from the ultrasonic velocity. P wave velocity and the normalized distance from the impact point follow an exponential decay relation. Other properties, such as the damage parameter, crack density, and attenuation coefficient, are expressed by a power law decay with distance. The damage parameter and attenuation coefficients are approximately linearly related. The slope of the linear fitting results in directions normal to the crack orientation is about twice the value in direction along the crack orientation. The attenuation coefficient is found to be a more useful parameter than elastic velocity in describing the anisotropic orientation of cracks.

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Additional Information:© 2007 by the American Geophysical Union. Received 16 February 2006; revised 30 July 2006; accepted 19 September 2006; published 9 January 2007. This research was supported by NASA Goddard grant under award NNG04GI07G. We appreciate the technical support of E. Gelle and M. Long. We thank G. Ravichandran for the use of the ultrasonic attenuation apparatus. We also thank Shiming Zhuang, Tracy Kidd, and Daoyuan Sun for their thoughtful suggestions and discussions. Division of Geological and Planetary Sciences, California Institute of Technology contribution 9128.
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Subject Keywords:granite; shockwave; crack and damage; ultrasonic velocity; attenuation
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Caltech Division of Geological and Planetary Sciences9128
Issue or Number:B1
Record Number:CaltechAUTHORS:20141022-085054442
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Official Citation:Ai, H. A., and T. J. Ahrens (2007), Effects of shock-induced cracks on the ultrasonic velocity and attenuation in granite, J. Geophys. Res., 112, B01201, doi:10.1029/2006JB004353
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50668
Deposited By: Tony Diaz
Deposited On:22 Oct 2014 16:25
Last Modified:10 Nov 2021 18:59

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