| Project/Area Number |
08640536
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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 | National Astronomical Observatory |
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Principal Investigator |
TAMURA Yoshiaki Division of Earth Rotation, reserch fellow, 地球回転研究系, 助手 (90150002)
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| Co-Investigator(Kenkyū-buntansha) |
HEKI Kosuke Division of Earth Rotation, associate professor, 地球回転研究系, 助教授 (30280564)
NAKAI Sinzi Division of Earth Rotation, associate professor, 地球回転研究系, 助教授 (70000172)
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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 |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1997: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1996: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Keywords | sea level change / tide gauge / tide gage / GPS / VLBI / co-location / sea level / tide gauge |
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| Research Abstract |
In recent 40 years, sea level lift of about 15cm or 20 cm is observed at the tide gauge stations (Miyako, Kamaishi, Ofunato and Ayukawa) along the Pacific coast in Tohoku area in Japan. The rate of sea level change is rather small in 1980s, while it becomes high in 1990s. To resolve global sea level change and regional crustal movement, the coordinates of the tide gauge stations were connected with a reference GPS bench mark in the National Astronomical Observatory, Mizusawa. The coordinates connection between tide gauge statins and Mizusawa was carried out using GPS.The GPS bench mark in Mizusawa was also connected with a fiducial point of the VLBI antenna in Mizusawa.
The daily repeatability of relative height between Mizusawa GPS bench mark and a tide gauge station is within 5 or 10mm. We recognized that we could obtain the precision of 2 or 3mm in vertical if we carried out two weeks continuous GPS observations. Also we found that the precision of GPS positioning could be improved by estimating the gradient of wet atmospheric delay in GPS measurements. The local tie between GPS bench mark and the VLBI fiducial point was carried out several times and the coordinates were reproduced with in 1mm error in horizontal and vertical.
We estimated that the half or two thirds of the observed sea level change in this area was caused by the regional crustal movement. We must consider the post-seismic movements of the reference bench marks to discuss long period phenomena such as sea level change, because we found that the aftership of Sanriku-Haruka-Oki earthquake caused long time and short time variation of GPS bench mark positions in Tohoku area (Heki and Tamura, 1997)
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