1987 Fiscal Year Final Research Report Summary
Real-Time Observation of Faulting Process in Rock by Seismic Computer Tomography
| Project/Area Number |
61460193
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
資源開発工学
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| Research Institution | Kyoto University |
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Principal Investigator |
TERADA Makoto Faculty of Engineering, Kyoto University, Professor, 工学部, 教授 (40025862)
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| Co-Investigator(Kenkyū-buntansha) |
YANAGIDANI Takashi Faculty of Engineering, Kyoto University, Instructor, 工学部, 助手 (00259128)
MATSUMOTO Yoshio Faculty of Engineering, Kyoto University, Instructor, 工学部, 助手 (00026022)
SAITO Toshiaki Faculty of Engineering, Kyoto University, Lecturer, 工学部, 講師 (90056151)
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| Project Period (FY) |
1986 – 1987
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| Keywords | Seismic CT / Seismic wave velocity / Anisotropy / Cluster of microcracks / Localization of dilatancy |
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| Research Abstract |
The seismic computer tomography (CT) was applied to observe how dialatancy (microcrack) localizes before fauting under uniaxial compression. By this technique, the distribution of P-wave velocity within a some sliced plane of the rock specimen can be mapped by analyzing the scanned travel times along a number of seismic ray paths. Because the velocities of seismic waves are influenced by the density, aspect ratio, and volume of microcracks along the transmitted path, the maps may be useful to see the process of faulting.
We applied seismic CT preliminarily to the specimen of Oshima granite, once uniaxially compressed to post-peak region and then recovered without crushing. The seismic CT was found to be a favorable technique to observe the localization of microcracks in rock. This seismic CT was improved with regard to the compensation for anisotropy of seismic velocity and the accuracy of measuring systems.
Finally, the seismic CT was applied to observe how dilatancy of rock localizes before faulting. The seismic CT can map the spatial distribution of P-wave velocities. Since P-wave velocity is determined by the extent of dilatancy, mapping the seismic profile is useful for observing non-destructively the progressive development of dilatancy. The specimen of Oshima granite was compressed at a constant deformation rate under uniaxial stress. The reconstructions were made within the plane perpendicular to the loading axis at several stress levels. The obtained maps clearly show the metamorphic changes of dilatancy before faulting.
On the other hand, we applied the seismic CT to visualize the water infiltration into dry granite and to characterize its presence. For the result, the behavior of water spreading through the interconnecting mecrocracks could be observed by reconstructing the seismic profiles.
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