All issues
Volume 50 (2004)
- Issue 4 Pages 245-
- Issue 3 Pages 187-
- Issue 2 Pages 53-
- Issue 1 Pages 1-
Volume 50, Issue 4
Displaying 1-4 of 4 articles from this issue
- |<
- <
- 1
- >
- >|
-
Tetsuro Kondo2004 Volume 50 Issue 4 Pages 245-262
Published: December 25, 2004
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSA very long baseline interferometry (VLBI) technique was originally developed to study radio source size and structure with high angle resolution by utilizing atomic clocks and magnetic recording systems. In the late 1970's VLBI came to be used for precise geodetic measure ments by the development of technique called bandwidth synthesis to measure group delays with sub-nanosecond accuracy. In the United States, VLBI system named Mark-III was devel oped for precise geodetic measurements and started operation. In the same period, satellite laser ranging (SLR) demonstrated its high-accuracy capability for geodetic measurements. NASA started the Crustal Dynamics Project (CDP) in 1979 to study the dynamic motion of the surface of the earth by using these space techniques. Since the accuracy of VLBI and SLR at that time was about 3 cm, a series of measurements spanning several years was expected to reveal actual plate motions with the formal velocity uncertainty less than 1 cm/year. In Japan, the Radio Research Laboratory (RRL) (presently NICT: National Institute of Information and Communications Technology) initiated VLBI and has led the technology developments from the beginning. NICT started the developments of the first VLBI system (K-1) in 1974, and carried out the first VLBI experiment in Japan successfully in 1977. This success led to the developments of precise VLBI system (K-3) for geodetic use, which is designed to be compatible with the Mark-III system. In 1983, NICT succeeded in the first Japan-US VLBI experiment using the K-3 system. NICT then joined regular CDP experiments with the K-3 system from 1984 to directly measure the motion of the Pacific plate. The motion of the Pacific plate was detected as early as in the next year. NICT then started to develop a new VLBI system named K-4 in 1987, which realized easy operation and transportation. K-4 was operated at Minamitorishima (Marcus Island), which is the only island in the Japanese territory located on the Pacific plate, and contributed to the direct measurements of the motion of the Pacific plate in Japan. Thereafter NICT has led the developments of VLBI in the world, such as real-time VLBI systems, gigabit recording VLBI systems, internet VLBI(e-VLBI) systems, and the standardization of the interfaces and software protocols.View full abstractDownload PDF (6146K) -
Deformation of Cased Circular Holes by Horizontal Stresses Working at Infinity and Internal PressureShoji Sakata2004 Volume 50 Issue 4 Pages 263-280
Published: December 25, 2004
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSCrustal deformation is routinely observed with borehole tiltmeters and/or strainmeters. In most cases a borehole tiltmeter is fixed to the borehole casing by a clamping device. When the borehole is deformed by external stress, the center of the vessel shifts from the origi nallocation, and this shift may cause a spurious tilt. To estimate this possible false tilt, we need an analytical method to calculate the deformation of cased boreholes under such condi tions. A borehole strainmeter, regardless of type, is installed into an open borehole with mortar or cement grouting, and we measure the deformation of the cylindrical vessel under the outer stress field. The relation between deformation of a cylinder and the stresses acting at infinity is important in the derivation of strain. The author treated two-layer models, composed of an inner metal cylinder and outer elastic medium, in his first paper regarding the Sakata-type three-component strainmeter (1981), in which the effects of casings, as well as formulas to express stress and displacement distributions were discussed. In this paper the method for two-layer models is applied to three-layer models, in which the intermediate grouting strata are considered. Coefficients in the formulas to describe the stress and displacement distributions are obtained by solving the simultaneous equations in the text. In addition the deformation of a metal cylinder submitted to fluid pressure on the inner surface is treated. The results may be applicable to estimate the effects of atmospheric pressure changes in boreholes that contain water.View full abstractDownload PDF (1207K) -
-An Obituary of Dr . Akihiko Sakuma -Tsuneya Tsubokawa2004 Volume 50 Issue 4 Pages 281-294
Published: December 25, 2004
Released on J-STAGE: September 15, 2005
JOURNAL FREE ACCESS -
Tsuyoshi Watanabe, Yuichi Imanishi2004 Volume 50 Issue 4 Pages 295-303
Published: December 25, 2004
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSDownload PDF (978K)
- |<
- <
- 1
- >
- >|