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Volume 46 (2000)
- Issue 4 Pages 239-
- Issue 3 Pages 177-
- Issue 2 Pages 89-
- Issue 1 Pages 1-
Volume 46, Issue 2
Displaying 1-4 of 4 articles from this issue
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Takeshi Matsumoto2000 Volume 46 Issue 2 Pages 89-108
Published: June 25, 2000
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSGravity measurement on the sea bottom is essential to detect the precise structure under neath the sea bottom and to estimate the density of sediment and bedrock. Measurement byuse of on-land survey systems on board the deep sea submersibles SHINKAI 2000 and SHINKAI 6500 was carried out in the tectonically active sites: in the southernmost part of the Toyama Trough and the adjacent Toyama Deep Sea Channel, over the two small knolls located in the southermost part of the "Fukaura Small Hills" off Oga Peninsula, in the WMARK area, western Mid Atlantic Ridge-Kane Transform intersection, etc. In these areas high-precision gravity anomalies higher than those expected from the surface-ship survey were obtained . Active tectonicsoccurring in these sites were discussed through the analysis of the obtained gravity data.View full abstractDownload PDF (5259K) -
Chinatsu Yonezawa, Shoji Takeuchi2000 Volume 46 Issue 2 Pages 109-124
Published: June 25, 2000
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSThe current space-borne C-band ERS-1/SAR and RADARSAT-I data were processed and analyzed experimentally for extracting interferometric fringe. Then the possibility for detecting crustal deformation in several Japanese test sites is discussed . As the result of interfero metric analysis of ERS-1/SAR data, baseline distance should be short for generating initialinterferogram. It is found that the fringe continuity and coherence are significantly affected by not only observation interval but also land cover conditions . That proves that C-band SAR interferometry are more sensitive to ground surface stability than L-band SAR . According to this sensitivity, damaged urban areas by Hyogoken-nanbu earthquake could be detected . Local phase difference change patterns are found from the multi data pairs which interval included the earthquake. The data pair observed in the eastern part of Saitama prefecture with 933 days interval also indicates local fringe patterns which correspond with precise leveling results. As the result of interferometric analysis for RADARSAT-I data, the conditions forextracting continuous fringe are estimated to be similar to that of ERS-1/SAR data . Although the selection of test sites and data pair are important to generate continuous fringe, C-band SAR interferometry is expected to estimate local deformation in urban area.View full abstractDownload PDF (11923K) -
Manabu Yatabe2000 Volume 46 Issue 2 Pages 125-148
Published: June 25, 2000
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSShapes of celestial bodies are governed by some forces: the self-gravitation, the centrifugal force due to the rotation, the tidal force, and so on. Assuming the hydrostatic equilibrium, the bodies tend to have spherically symmetric shapes under the self-gravitation alone. The re maining forces except the self-gravitation cause departures from the spherical symmetry. Anacceleration field, which is subtracted the self-gravitation from the gravity field, is referred to as the residual gravity field, and is formulated in this study. Regarding the physical surfaces of the bodies as equipotential surfaces, the deformations of the shapes due to the residual gravity are discussed based on the hydrostatic equilibrium. As an application of the formulation, the Mercury's shape is considered by using the relation between the core flattening and the zonal harmonic coefficient J2. It is predicted that Mercury has an almost spherical shape.View full abstractDownload PDF (1781K) -
Sachiko Iwano, Yoichi Fukuda2000 Volume 46 Issue 2 Pages 149-152
Published: June 25, 2000
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSIn order to get precise Bouguer anomalies, terrain correction is very important. Especially for so called micro gravity surveys, which have been widely applied for various purposes recently, the accuracy of the terrain correction seriously de pends on the grid size of Digital Elevation Model (DEM). We thus studied the relation between the accuracy of the terrain correction and the DEM employed for the calculation with a special attention of its spatial resolution. Practically, the 50 mintervals DEM (50 mDEM) published by the Geo graphical Survey Institute have been widely used for gravity terrain correction in Japan . We there fore decided to estimate the accuracy of terrain correction using 50 mDEM as one of the standard cases. We made 10 mDEM from 1/2, 500 city planning maps and compared the two Bouguer gravity anomalies obtained by using the 50 mDEM and the10 mDEM, respectively. The result shows that about 0.2 mgal or a better terrain correction can be obtained only by using the 50 mDEM in topographically flat areas. However, we need more detailed terrain data in topographically steep mountain areas, or even in flat areas to achieve accurate terrain correction of better than 0.1 mgal.View full abstractDownload PDF (540K)
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