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Volume 56 (2010)
- Issue 4 Pages 125-
- Issue 3 Pages 101-
- Issue 2 Pages 47-
- Issue 1 Pages 1-
Volume 56, Issue 3
Displaying 1-3 of 3 articles from this issue
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TECHNICAL REPORT
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Yusaku Ohta, Satoshi Miura, Shinsuke Matsumura, Toshiyuki Mori2010 Volume 56 Issue 3 Pages 101-106
Published: 2010
Released on J-STAGE: March 30, 2012
JOURNAL FREE ACCESSWe developed a GPS observation system using the combination of a low-cost GNSS receiver and a LINUX data logger for the crustal deformation monitoring. We implemented three functions on the system. The first one is the data logging of GNSS streaming data, the second one is controlling the GNSS receiver, and the last one is conversion to RTCM format that is streamed by means of TCP/IP for RTK-GPS processing. We assessed the GPS data quality by two kinds of tests. At first, we checked the zero-baseline kinematic post-processing using 20Hz sampling data obtained by an expensive geodetic-level receiver and our newly developed system. The standard deviations of the resulting time series are 0.85 mm (EW), 1.17 mm (NS), and 1.62 mm (UD), respectively. Next, we tested the long-baseline (178.5 km) real-time kinematic analysis. We conclude that our new GPS observation system has functions and capabilities comparative to expensive geodetic-level receivers used for the crustal deformation monitoring with inexpensive costs.View full abstractDownload PDF (475K)
ORIGINAL PAPER
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Akio Katsumata, Takeyasu Yamamoto, Akio Kobayashi, Nobuo Hamada, Sumio ...2010 Volume 56 Issue 3 Pages 107-116
Published: 2010
Released on J-STAGE: March 30, 2012
JOURNAL FREE ACCESSWe evaluated the crustal deformation detection level of a long-baseline laser extensometer in the time domain through the power spectrum from time-series data. The extensometer was newly installed in Hamamatsu City, Shizuoka Prefecture, Japan, and has a 200 m baseline. The detection level was compared with those of borehole multicomponent strainmeters and the GPS network evaluated in our earlier study, and also compared with noise levels of other laser extensometers. The power spectrum of the laser extensometer data shows a lower amplitude level by about 100.5 and a frequency dependence similar to the average for borehole multicomponent strainmeters. The frequency dependence and amplitude of the noise level are comparable to those of long-baseline laser strainmeters in other regions. These results imply that the laser extensometer would detect the crustal deformation due to the Tokai long-term slow-slip event earlier than the GPS network.View full abstractDownload PDF (500K) -
Koichiro Doi, Hiroshi Ikeda, Yuichi Aoyama, Kazuo Shibuya2010 Volume 56 Issue 3 Pages 117-124
Published: 2010
Released on J-STAGE: March 30, 2012
JOURNAL FREE ACCESSChange of the liquid helium level affects the position change of the proof mass of superconducting gravimeter (SG). We estimated its effect on three different types of SGs (TT-70#016, CT#043, and OSG#058) by approximating the spatial relationship between the SG sensor unit and liquid helium reservoir using a double-layered cylinder model where the inner cylinder and outer one are assumed SG sensor unit and liquid helium reservoir tank, respectively.
From these calculations, it was predicted for SG TT-70#016 that a gravity change of 0.88 µGal (1 µGal=10-8m•s-2) results when the liquid helium level in the reservoir is increased from 0% to 100%. Similar gravity changes of 0.25 µGal and 0.35 µGal were also predicted for SGs CT#043 and OSG#058, respectively. In addition, artificially-induced, rapid gravity changes of approximately 0.9 µGal over the course of two hours likely occur during the filling of SGs with liquid helium from 20% to 100% for TT-70#016. Actual gravity changes correlated with the rapid liquid helium level changes were also found in the observed gravity record of SG CT#043 in 2003, although the actual gravity changes were greater than the predicted ones.
Gravity changes of approximately 0.1 µGal due to fluctuations of 5% to 14% in the liquid helium level change are also possible during the normal continuous observation with SGs. It is therefore preferable to monitor the liquid helium level routinely when measuring small gravity signals in the order of sub-micro Gal to correct for these effects.View full abstractDownload PDF (300K)
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