Journal of the Geodetic Society of Japan

Consideration on the Relationship between Temporal Changes of Gravity and Leveled Heights and its Application to Tectonic Regions

Minoru Tanaka

2003 Volume 49 Issue 3 Pages 159-175
Published: September 25, 2003
Released on J-STAGE: March 01, 2011

DOIhttps://doi.org/10.11366/sokuchi1954.49.159

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From the relationship between temporal changes of gravity and leveled heights in tec tonic region, a new practical equation for detecting temporal change in orthometric height, which provides unstable modes of vertical crustal movement in a special case, i.e., orthometric height decay instability caused by growing gravity variation, is presented. This instability generates at the time of the maximum growing geoid level so as to stabilize the geopotential in the area and to regulate further crustal upheaval and returns from the high unstable level to the initial linear stable level, generating the earthquakes around the zone of increasing geoidal undulation. By making some assumptions to solve this equation, unstable fluctuation mode and strong instability mode were estimated to occur with periods of 15-17 years and 44-46 years, respectively, basing on the 7-8 year phase difference of crustal deformation under the assumption of the earthquake recurrence period of 117 years in the Nankai-Tokai zone. It is pointed out that the occurrence mode of the large anomalous crustal deformation, which may be related to the great earthquake, can be, conversely, estimated by the sequential mode analyses from these superposed instability modes within a few years deviation.

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Determination of Absolute Gravity Values using a FG 5#210 in Bandung and Yogyakarta, Indonesia

Toshihiro Higashi, Yoichi Fukuda, Maiko Abe, Shuzo Takemoto, Sjafra Dw ...

2003 Volume 49 Issue 3 Pages 177-180
Published: September 25, 2003
Released on J-STAGE: July 05, 2011

DOIhttps://doi.org/10.11366/sokuchi1954.49.177

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In November 2002, we carried out absolute gravity measurements for the first time in Bandung and Yogyakarta, Indonesia. We could success fully obtain the absolute gravity values for the two gravity stations. The gravity value deter mined for Bandung is 977976701.2 ± 0.1 μ gal (1, i gal= 10^-8 ms^-2) and that for Yogyakarta is 978203093.5±0.4, μgal. Determined absolute gravity values will contribute not only to the establishment of a precise gravity network in Indonesia but also to the detecting of gravity changes caused by seismic and volcanic activities.

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Correction Vectors for Island Positions in Tokyo Datum

Mikio Tobita, Hiromichi Tsuji, Yasuhiro Takahashi, Toshio Kawahara

2003 Volume 49 Issue 3 Pages 181-192
Published: September 25, 2003
Released on J-STAGE: September 07, 2010

DOIhttps://doi.org/10.11366/sokuchi1954.49.181

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Correction vectors from coordinates in datum sheet to coordinates surveyed by static GPS at 57 Japanese islands in Tokyo Datum are calculated and compiled. The magnitude of the corrections of Iwo-jima, Daito-jima, Tarama-jima, Ishigaki-jima, and Yonaguni-jima islands exceeds 200 m, because the coordinates in datum sheet in Tokyo Datum were determined by astronomical survey of several tens of years ago. The correction vectors represent internal consistency in Tokyo Datum and can be used for corrections of island maps in Tokyo Datum, e.g., maps in car navigation systems.

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Report on the EGS-AGU-EUG Joint Assembly and the State of GPS Vertical Positioning Precision Workshop

Yuusaku Ohta

2003 Volume 49 Issue 3 Pages 193-194
Published: September 25, 2003
Released on J-STAGE: September 07, 2010

DOIhttps://doi.org/10.11366/sokuchi1954.49.193

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