A model of acoustic pulse propagation and its application to determine Q for a rock mass

Kavetsky, A.; Chitombo, G.; McKenzie, C.K.; Yang, Rongzhou

doi:10.1016/0148-9062(90)90006-n

Cited by 14 publications

(7 citation statements)

References 11 publications

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“…(15)). As was mentioned in the previous subsection, the value of c depends on the experimental details and on how the pulse rise time is measured (BLAIR, 1990;KAVETZKY et al, 1990). Equation (17) always remains valid, however, provided the relation between pulse rise time and Q v has the form described by eq.…”

Section: Enhanced Velocity Tomographymentioning

confidence: 99%

“…Stronger damping of the high-frequency part of the signal spectrum can be seen as a broadening of the recorded pulse or equivalently as an increase of the pulse rise time. This broadening has been found to be related to the Q and v factors as follows (KAVETZKY et al, 1990;GLADWIN and STACEY, 1974):…”

Section: Pulse Broadening Attenuation Tomographymentioning

confidence: 99%

“…The constant c depends on the type of source (BLAIR and SPATHIS, 1984;GLADWIN and STACEY 1974;KAVETZKY et al, 1990) and on how t rt is de®ned. If the standard de®nition of t rt as the time when the pulse amplitude changes from 10% to 90% of the pulse maximum amplitude is used, then c $ 0:5 (BLAIR, 1990;KAVETZKY et al, 1990). The spatial distribution of Q can be derived from eq.…”

Section: Pulse Broadening Attenuation Tomographymentioning

confidence: 99%

“…This accuracy of travel-time picking is acceptable for velocity tomography but must be essentially improved for pulse rise time data to make Q tomography possible. Improvement may be achieved by measuring the pulse rise time, not as the dierence between ®rst arrival and pulse maximum arrival times, but as the time when the pulse amplitude changes from 10% to 90% of the pulse maximum amplitude (BLAIR, 1990;KAVETZKY et al, 1990). This method allowed measurement of the rise time with an accuracy of about 0.02 ls which gave relative errors of about 1±2%.…”

Section: Datamentioning

confidence: 99%

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Tomographic Imaging of Thermally Induced Fractures in Granite Using Bayesian Inversion

Deçbski¹,

Young

2002

Pure appl. geophys.

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Ð The internal structure of rock samples studied in laboratory experiments can be described by a variety of physical parameters. Some of them, like the velocity of acoustic waves, enhanced velocity or quality factor can be reconstructed by means of ultrasonic tomography. This article presents the results of classical velocity tomography imaging, accompanied by the results of attenuation tomography and recently introduced enhanced velocity tomography obtained for a Lac Du Bonnet granite sample subjected to thermal stresses. To invert acoustic data recorded during six heating cycles, a Bayesian inversion scheme accompanied by a genetic algorithm optimization approach and the robust Cauchy norm have been used. To obtain the highest possible spatial resolution of images the inversion was performed in two steps. In the ®rst step a crude parameterization of the sample was used. The result of this stage was next taken as an a priori model for a ®nal inversion with re®ned parameterization. The choice of parameterization (cell sizes) and damping parameters at both stages was based on an analysis of the resolution operator. Both velocity and enhanced velocity tomography accurately imaged changes in the rock microstructure caused by thermal stresses. However, enhanced velocity tomography gave a much better spatial resolution than velocity tomography. On the other hand, attenuation tomography based on inversion of pulse rise times was able to image only a rough structure of the sample and it has diculty with reasonable imaging of the crack formed in the sixth heating cycle.

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Section: Enhanced Velocity Tomographymentioning

confidence: 99%

Section: Pulse Broadening Attenuation Tomographymentioning

confidence: 99%

Section: Pulse Broadening Attenuation Tomographymentioning

confidence: 99%

Section: Datamentioning

confidence: 99%

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Tomographic Imaging of Thermally Induced Fractures in Granite Using Bayesian Inversion

Deçbski¹,

Young

2002

Pure appl. geophys.

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“…If a pressure pulse is used as a source wavelet, then the spectrum change manifests itself in a pulse rise time broadening along a ray path. This broadening has been found to be related to the quality fac- (2) where the integral is taken along a ray path, c is some constant depended on a source characteristic (c ,• 0.5) [Blair and Spathis 1984;Kavetzky et al 1990] and to is the 'pure' source pulse rise time. Using this approach estimation of Q requires a very stable source of acoustic pulses to assure the same to and c for all source-receiver pairs.…”

Section: Enhanced Velocity Tomographymentioning

confidence: 99%

Enhanced velocity tomography: Practical method of combining velocity and attenuation parameters

Dębski

Young

1999

Geophysical Research Letters

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Abstract. Acoustic (ultrasonic) tomography is now a well acepted method for investigating the internal structure of rock samples and rock masses. In this article we describe a new parameter to be imaged, which combines the robustness of velocity tomography and the sensitivity of attenuation tomography resulting in Enhanced Velocity Tomography. The theoretical considerations are illustrated by a computer simulation and then by application to data from a granite sample subjected to induced damage by heating. In both cases the Enhanced Velocity Tomography is found to be more sensitive to the internal rock structure than classical velocity tomography and overcomes instability problems characteristic of attenuation tomography.Velocity and the quality factor are the most intuitive pa-

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Tomographic Imaging of Thermally Induced Fractures in Granite Using Bayesian Inversion

Dębski

Young

2002

The Mechanism of Induced Seismicity

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A model of acoustic pulse propagation and its application to determine Q for a rock mass

Cited by 14 publications

References 11 publications

Tomographic Imaging of Thermally Induced Fractures in Granite Using Bayesian Inversion

Tomographic Imaging of Thermally Induced Fractures in Granite Using Bayesian Inversion

Enhanced velocity tomography: Practical method of combining velocity and attenuation parameters

Tomographic Imaging of Thermally Induced Fractures in Granite Using Bayesian Inversion

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