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Volume 59 (2013)
- Issue 4 Pages 133-
- Issue 3 Pages 63-
- Issue 2 Pages 25-
- Issue 1 Pages 1-
Volume 59, Issue 2
Displaying 1-3 of 3 articles from this issue
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TECHNICAL REPORT
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Hiroshi Ikeda, Kazunari Nawa, Yuichi Imanishi2013 Volume 59 Issue 2 Pages 25-36
Published: 2013
Released on J-STAGE: July 11, 2015
JOURNAL FREE ACCESSWe started a superconducting gravimeter observation to elucidate relationships between slow slip events and gravity changes at Ishigakijima near Ryukyu trench, southwestern Japan in February 2012. Before the installation of the superconducting gravimeter (CT-36) at Ishigakijima, we refurbished the CT-36, installed at the Inuyama observatory of Nagoya University originally, so that the system can operate reliably at such a remote island. Specifically, for the planned observation, we replaced the compressor for the refrigerator from ‘water-cooled’ type to ‘air-cooled’ type. In addition, at University of Tsukuba, we warmed up the Dewar to room temperature to remove the ‘clogs’ inside it. This resulted in eliminating strange behaviors in the temperature controls of the gravimeter, as well as solving the problem in transferring liquid helium into the Dewar. During these refurbishment processes, the frequency responses and the instrumental drift of CT-36 were also measured. As a result, it was verified that CT-36 works ideally as a high-precision long-term gravimeter.View full abstractDownload PDF (1667K) -
Toshihiro Higashi, Koichiro Doi, Hideaki Hayakawa, Takahito Kazama, Ha ...2013 Volume 59 Issue 2 Pages 37-43
Published: 2013
Released on J-STAGE: July 11, 2015
JOURNAL FREE ACCESSAbsolute gravity measurements were carried out as a part of activities in 2011-2012 austral summer season of the 53rd Japanese Antarctic Research Expedition (JARE53) at Syowa Station, Antarctica. Obtained absolute gravity value was 982524322.7±0.1 μgal (1 μgal=10-8ms-2) using an absolute gravimeter FG5#210. Absolute gravity measurements using FG5 gravimeter have been conducted 5 times at Syowa Station. Comparing the previous obtained gravity values, we had confirmed instrumental offset among employed three FG5 absolute gravimeters. The gravity values after the correction of instrumental offset show a gravity decreasing rate of about 0.24 μgal/year. This secular gravity changes are consistent with the crustal uplift associated with Glacial Isostatic Adjustment (GIA) observed around Syowa Station, Antarctica.View full abstractDownload PDF (8321K)
ORIGINAL PAPER
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Mika Arimoto, Yo Fukushima, Manabu Hashimoto, Youichiro Takada2013 Volume 59 Issue 2 Pages 45-56
Published: 2013
Released on J-STAGE: July 11, 2015
JOURNAL FREE ACCESSIn order to precisely measure the land subsidence in Semarang, Indonesia, we performed a smallbaseline interferometric synthetic aperture radar (SAR) time-series analysis using the images acquired by the Japanese Advanced Land Observing Satellite (ALOS). We used a total of 34 SAR images, acquired from both the ascending and descending orbits, and obtained the subsidence timeseries in the two line-of-sight (LOS) directions. Before solving for the displacement time-series, we corrected for artifacts due to orbital inaccuracies and atmospheric phase delay. We obtained the time-series of quasi-vertical displacements by decomposing the displacement time-series in the two LOS directions. The result shows that the subsidence is limited on low-land areas where an aquifer system is well developed, suggesting that the cause of the subsidence is extraction of water from the aquifer. The subsidence rate was estimated to be practically constant with time with no clear seasonal effects. The maximum subsidence rate of 10±0.4 cm/year was obtained at a location where subsidence had not been identified before. Our study also shows the effectiveness of L-band SAR data to monitor land subsidence over time.View full abstractDownload PDF (10761K)
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