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Rock fracture compliance derived from time delays of elastic waves |
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| Authors: | M Möllhoff CJ Bean PG Meredith |
| Institution: | 1. Seismology and Computational Rock Physics Laboratory, UCD School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland;2. Complex and Adaptive Systems Laboratory (CASL), University College Dublin, Belfield, Dublin 4, Ireland;3. Rock & Ice Physics Laboratory, Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, UK |
| 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. |
| Keywords: | Compliance Fracture Time delay Transmission coefficient Ultrasonic |