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Real-Time Observation of Faulting Process in Rock by Seismic Computer Tomography

地震计算机断层扫描实时观测岩石断裂过程

基本信息

批准号：
61460193
负责人：
TERADA Makoto
金额：
$ 2.88万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1987
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-61460193/
关键词：
Seismic CT Seismic wave velocity Anisotropy Cluster of microcracks Localization of dilatancy 弾性波CT 岩石の異方性 P波速度とマイクロクラック

项目摘要

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.

应用地震计算机断层扫描（CT）观察了单轴压缩下断裂前的微裂纹局部化过程。利用该技术，通过分析沿若干地震射线路径的扫描传播时间，可以绘制出岩石试样某一切片平面内的纵波速度分布。由于地震波的速度受传播路径上微裂缝的密度、纵横比和体积的影响，这些图可能有助于了解断层的过程。我们对大岛花岗岩试样进行了初步的地震CT处理，在单轴压缩至峰后区域后恢复原状。地震CT是观察岩石微裂纹局部化的一种较好的方法。该方法在地震速度各向异性补偿和测量系统精度方面进行了改进。最后，应用地震CT观察岩石在断裂前的局部剪胀情况。地震CT可以绘制纵波速度的空间分布。由于纵波速度是由剪胀的程度决定的，因此绘制地震剖面对于非破坏性地观察剪胀的渐进发展是有用的。大岛花岗岩试样在单轴应力作用下以恒定变形速率压缩。在几个应力水平下，在垂直于加载轴的平面内进行重建。所获得的图清晰地显示了断裂前的扩容变质变化。另一方面，我们应用地震CT可视化水渗入干燥花岗岩并表征其存在。结果表明，通过重建地震剖面，可以观察到水在相互连接的微裂缝中的扩散行为。