Journal of the Geodetic Society of Japan

Calibration of the Scale Factor of Superconducting Gravimeter at Esashi using an Absolute Gravimeter FG5

Tadahiro Sato, Yoshiaki Tamura, Shuhei Okubo, Shigeo Yoshida

1996 Volume 42 Issue 4 Pages 225-232
Published: February 25, 1997
Released on J-STAGE: July 05, 2011

DOIhttps://doi.org/10.11366/sokuchi1954.42.225

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We have carried out a comparison measurement of the superconducting gravimeter (SG) #007 installed at Esashi Earth Tide Station (latitude: 39°08'53" N, longitude: 141°20'07" E, and altitude: 393 m) with an absolute gravimeter FG5 #109 for five days from May 25 to 29, 1996. From this comparison, we obtained a value of -56.334±0.118 μ Gal/V (1 μ Gal= 10-8 ms-2) as the scale factor of SG #007. We have also confirmed that the previously adopted scale factor (-56.234μGal/V), which was determined by LaCoste & Romberg gravimeters, is consistent with the value calibrated using FG5 #109 within the discrepancy of about 0.2%. Reliability of the calibration using FG5 absolute gravimeter was examined by comparing two measurements at Esashi with predicted gravity tides; the measurement with FG5 #109 in this time and that with FG5 #102 in 1993, which was conducted by NOAA (National Oceanographic and Atmospheric Administration) of the USA. The comparison results suggest that it is enough possible to calibrate the SG using FG5 gravimeters at an accuracy better than 1%.

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An Estimate of the Philippine Sea Plate Motion Derived from the Global Positioning System Observation at Okino Torishima, Japan

Teruyuki Kato, Yoshiko Kotake, Toshikazu Chachin, Yuzaburo Iimura, Shi ...

1996 Volume 42 Issue 4 Pages 233-243
Published: February 25, 1997
Released on J-STAGE: September 07, 2010

DOIhttps://doi.org/10.11366/sokuchi1954.42.233

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Okino Torishima (Parece Vela) is an isolated island located in the midst of the Philippine Sea plate. Different from other islands in the plate, the island is not contaminated by either local volcanic activity or non-rigid deformation near plate boundary. Thus, monitoring of its displacement may represent rigid motion of the plate. A series of GPS observations at this island with other peripheral sites have been conducted since 1989. We have analysed recent data of 1992, 1944, 1995 and 1996, since precise orbits are available only for these observations. Tsukuba was assumed to be moving according to ITRF93 velocity field. Displacement of Okino Torishima by this assumption suggests that the island is moving toward WNW with a rate of Vns=1.08(±0.81)cm/yr and Vew=-2 .77(±1.04)cm/yr or 2.97(±1.07)cm/yr toward N68.7(±16.1)°W. Taking recent estimate of local velocity of Tsukuba relative to the stable Eurasian plate by Heki (1996) into account, the velocity of Okino Torishima relative to Eurasian craton is estimated to be Vns=3.00(±0.84)cm/yr and Vew=-5.17(±1.06)cm/yr. This result is well consistent with the velocity estimated from seismic slip vectors by Seno et al. (1993) (Vns=2.87 cm/yr, Vew=-5.81 cm/yr). The present result seems to suggest that the Philippine Sea plate is moving steadily at least in the recent hundreds of years.

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International Symposium on Gravity, Geoid and Marine Geodesy 1996

Jiro Segawa, Sinzi Nakai, Yoichi Fukuda, Hiromi Fujimoto

1996 Volume 42 Issue 4 Pages 245-261
Published: February 25, 1997
Released on J-STAGE: September 07, 2010

DOIhttps://doi.org/10.11366/sokuchi1954.42.245

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