| Project/Area Number |
13640417
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 | The University of Tokyo |
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Principal Investigator |
ARAYA Akito Earthquake Research Institute, Research Associate, 地震研究所, 助手 (30272503)
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| Co-Investigator(Kenkyū-buntansha) |
OTAKE Yuji Earthquake Research Institute, Research Associate, 地震研究所, 助手 (60282729)
OKUBO Shuhei Earthquake Research Institute, Professor, 地震研究所, 教授 (30152078)
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| Project Period (FY) |
2001 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥4,100,000 (Direct Cost: ¥4,100,000)
Fiscal Year 2002: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2001: ¥3,200,000 (Direct Cost: ¥3,200,000)
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| Keywords | gravimeter / laser / interferometer |
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| Research Abstract |
Gravity observations bring us useful underground information on the movement of the matters such as the magma and the ground water. Absolute gravimeters play an important role on this gravity observation, without constructing any reference points.
Current absolute gravimeters, however, have difficulties in their large size and price for the widespread observation in the field. We have noticed the data acquisition and the signal analyzes in the absolute gravimeter, and reached perspectives for small-size absolute gravimeters. Results of this study are summarized as follows.
(1) We have proposed a micro-distance toss-up type absolute gravimeter. In this method, we formalized how the toss-up distance and a sampling rate of the signal detection are related to the accuracy of the measured gravity. As a result, the toss-up distance of 2mm and the sampling rate of 1MHz are sufficient to detect gravity in 1-μgal accuracy.
(2) Acceleration of the ground is another noise source of the gravity measurements. In order to reduce the ground noise, we have considered to use an acceleration signal which is obtained from the feedback system controlling a reference mirror ; the acceleration signal is used to remove the ground noise from the observed gravity data. With the designed feedback system, the ground noise could be reduced smaller than 1 μgal.
(3) We have designed and fabricated a toss-up mechanism. Although the toss-up distance had enough reproducibility, we found a little rotation of the thrown mirror. It is caused by vibration of the thrower, and now we are re-designing the toss-up mechanism which applies little vibration on the thrown mirror.
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