| Project/Area Number |
08454121
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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 |
固体地球物理学
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| Research Institution | Nagoya University |
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Principal Investigator |
YAMADA Isao Faculty of Science Nagoya University, 理学部, 教授 (60022670)
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| Co-Investigator(Kenkyū-buntansha) |
ARAYA Akito University of Tokyo, Earthquake Research Institute, 地震研究所, 助手 (30272503)
SUDA Naoki Graduate School of Science, 大学院・理学研究科, 助手 (10222069)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥6,000,000 (Direct Cost: ¥6,000,000)
Fiscal Year 1997: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1996: ¥4,600,000 (Direct Cost: ¥4,600,000)
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| Keywords | laser interferometer / stabilized laser / surface waves / Earth's free oscillations |
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| Research Abstract |
Observations of seismic surface waves and Earth's free oscillations give precious informationon internal structure of the Earth. However, seismic data that have mainly been analyzed are vertical component since horizontal components usually contain very large low-frequency noise originated from ground tilting. We have investigated the origin of horizontal component noise in another research and have found that it has a strong correlation with atmospheric pressure variation. It seems that pressure loading gives rise to ground tilting. Therefore the horizontal component noise is inevitable as long as we use seismometers with pendulum.
This research was aimed to observe seismic surface waves and Earth's free oscillations using a high-precision laser interferometer, which is free from the noise observed in seismometer records. The results are as follows :
1.Iodine-stabilized Nd : YAG laser system was developed to use for a laser interferometer. Frequency stability of 1O^<13> were achieved.
2.Vacuum system with two chambers and pipes connecting them was developed to contain interferometer system. Compensation mechanism using 4 bellows was adopted to avoid the effect of atmospheric pressure variations. To maintain a vacuum of 1O^<-6> Torr we used a turbo-molecular pomp system. Length of interferometer base line is about 15m length.
3.The laser interferometer system was installed at Inuyama observation station of Nagoya University, It is now ready to observe seismic surface waves and Earth's free oscillations excited by large earthquakes.
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