2005 Fiscal Year Final Research Report Summary
A Research on the Mechanisms of the Temporal Change in Geophysical Parameters in an Underground Environment
| Project/Area Number |
15360474
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Earth system and resources enginnering
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| Research Institution | The University of Tokyo |
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Principal Investigator |
SANO Osam The univ. of Tokyo, Earthquake Research Institute, Professor, 地震研究所, 教授 (20127765)
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| Co-Investigator(Kenkyū-buntansha) |
UTADA Hisashi The univ. of Tokyo, Earthquake Research Institute, Professor, 地震研究所, 教授 (70134632)
FUKAO Yoshio JAMSTEC, Inst. Res. Earth Evolution, Director, 地球内部変動研究センター, センター長 (10022708)
TAKEI Yasuko The uni. of Tokyo, Earthquake Research Institute, Associate Professor, 地震研究所, 助教授 (30323653)
NAKAO Shigeru Kagoshima Univ., Faculty Science, Associate Professor, 理学部, 助教授 (90237214)
OGAWA Tsutomu The univ. of Tokyo, Earthquake Research Institute, Research, Professor, 地震研究所, 助手 (00345175)
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| Project Period (FY) |
2003 – 2005
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| Keywords | Precise Monitoring of Sound Velocity / Crustal Movement / Underground Environment / Small Stress Change / Mass and Heat Transfer |
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| Research Abstract |
To monitor very long-term stability and shield efficiency associated with underground construction is one of the important techniques in engineering field. In such a long-term monitoring, temporal change in observation parameters should be very small. Consequently, instruments with very high resolution and stability should be required for observation. In the Earth sciences, underground vault has been used for measuring very small change in strain and tilt of the ground, because underground is almost free from meteorological disturbances. However, because of their high resolution, the instruments for crustal deformation can easily detect possible effects of meteorological disturbances. Because of heterogeneity nature of surrounding rock, it is often difficult to determine major processes for such very small disturbances. French colleagues have an underground laboratory on the shores of the Roselend lake of which the annual variation in the water level is about 60 m in average. Such a la
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rge change in water level should bring significant change in stress field in surrounding rock of the vault and can be used for calibration of the observations. This study is focused on a development of precise measurement of sound velocity for estimating small stress change around a vault by the shores of the Roselend lake, Savoie, France. As the test site locates in the Alps mountain area and is not easily access in winter season due to heavy snowfall. It was needed to develop maintenance free system. In order to assure high stability in the measurement, the pulse generator was phase-locked with highly accurate OCXO by which the base clock of the digital oscilloscope was calibrated at the same time. The continuous measurement started in October 2004 and stopped in April 2006. The travel-time of the pulse was determined within the resolution of several ppm. Annual change in the travel-time was found to be about 1000 ppm. The correlation between the temporal change in water level and the travel-time was found good. However, phase shift was found, which indicates that the role of water in underground must be considered. Less
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Research Products
(6 results)
