All issues
Volume 56 (2010)
- Issue 4 Pages 125-
- Issue 3 Pages 101-
- Issue 2 Pages 47-
- Issue 1 Pages 1-
Volume 56, Issue 2
Displaying 1-3 of 3 articles from this issue
- |<
- <
- 1
- >
- >|
TECHNICAL REPORT
-
Teruhiro Yamaguchi, Minoru Kasahara, Hiroaki Takahashi, Muneo Okayama, ...2010 Volume 56 Issue 2 Pages 47-57
Published: 2010
Released on J-STAGE: March 30, 2012
JOURNAL FREE ACCESSWe have developed an easy-to-use Crustal Deformation Database (CDD) for strain, tilt and other long-term geophysical data. WWW-based user interface is employed for operations and the servers are connected to internet. Anyone who has internet connections and web browser, therefore, are easily possible to refer and download data from anywhere. We have adopted the WIN format (de facto standard format for the seismic data exchange in Japan) for data acquisition and management, because it can treat any sampling interval data without re-sampling procedure during data processing.
This database has following functions; 1) data drawing on the display for selected period from 1 second to 10 years, 2) data download for selected channels and period, and 3) several data analyses, i.e., filtering, tidal analysis by BAYTAP-G program, plane strain analysis and its linkage to seismic data.
Trial run of CDD is in operation from 2004 and 66 stations data operated by Hokkaido University, Tohoku University, University of Tokyo, Nagoya University, Kyushu University, Tono Research Institute of Earthquake Science, Geological Survey of Hokkaido and National Astronomical Observatory of Japan have been stored to CDD in real time and above functions are in use. We hope any institutions operating crustal deformation observation will join our CDD network to establish unified CDD of Japan.View full abstractDownload PDF (1081K)
ORIGINAL PAPER
-
—Partly Estimation for the First-order Leveling in Japan—Yuki Kuroishi2010 Volume 56 Issue 2 Pages 59-72
Published: 2010
Released on J-STAGE: March 30, 2012
JOURNAL FREE ACCESSWe quantitatively estimate the corrections for astronomical tides and ocean tidal loading to first-order leveling survey in Japan along its typical routes. Tidal force of the astronomical bodies such as the Moon and the Sun makes the geopotential surfaces and the deformable Earth’s surface tilt differently in both permanent and periodical manners. The force also redistributes the oceanic masses as ocean tides, producing differential tilts between those surfaces through their direct gravitational effects and load-induced elastic bending of the crust. Those differential tilts may affect the readings of spirit leveling only slightly, but may yield significant changes in orthometric heights on a national/ continental scale. The results show that temporally changing parts of the cumulative effects of astronomic tides along the routes are comparable to or even larger than, but not linearly related to their permanent parts, that those total cumulative effects possibly enlarge closure errors in loops, and that the cumulative effects of ocean tidal loading are generally minor but may become significant towards the ocean in high tide areas. The inclusion of astronomical tidal corrections in the analysis of nationwide precise leveling will be worthwhile in future for improvement in comparison of geoidal undulations among GPS/leveling data and gravimetric geoid models and for accuracy enhancement of the national height datum.View full abstractDownload PDF (2068K) -
Takeshi Katagi, Manabu Hashimoto2010 Volume 56 Issue 2 Pages 73-85
Published: 2010
Released on J-STAGE: March 30, 2012
JOURNAL FREE ACCESSWe evaluate the effect of the viscoelasticity in the upper mantle, especially possible viscous wedge mantle, on the postseismic deformation, by comparing the displacements following the 2004 Sumatra-Andaman earthquake obtained by continuous GPS during three and a half years. A three-dimensional finite element model is constructed to incorporate three dimensional heterogeneous structures considering the active back-arc opening in the Andaman Sea.
The results show that large postseismic displacements observed at GPS sites in Thailand, can be explained only by viscoelastic relaxation with a mantle viscosity ranging 5-10×1018 Pa s, except for the first six months. Postseismic displacements during the first six months may be caused by other mechanisms such as afterslip. Postseismic displacements computed for models with a zone of extremely low viscosity, which is expected from the active back-arc spreading in Andaman Sea, are inconsistent with the observed ones. This result implies the viscosity in the mantle wedge is not significantly lower than that in the surrounding mantle.View full abstractDownload PDF (1285K)
- |<
- <
- 1
- >
- >|