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Volume 28 (1982)
- Issue 4 Pages 193-
- Issue 3 Pages 121-
- Issue 2 Pages 73-
- Issue 1 Pages 1-
Volume 28, Issue 2
Displaying 1-4 of 4 articles from this issue
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Michio YANAGISAWA1982 Volume 28 Issue 2 Pages 73-81
Published: September 30, 1982
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSThe purpose of the present study is to clarify the crustal tilt generated by loads of ocean tide on the basis of the data obtained at the Aburatsubo Crustal Movement Obser vatory. The relation between the seiche in Aburatsubo Bay and the concerning crustal tilt at the Aburatsubo Observatory has been already reported in the previous paper . The observations were carried out by four sets of TEM-tiltmeters at the vault of the observatory and the oceanic data was obtained at the Aburatsubo tide station (G.S.I.) during the period from January 1979 to June 1980. The amplitude of tilt generated by loads of ocean tide for each tidal component is empirically determined as a function of the distance from the coast line on the basis of the results of observations. The amplitude ratio of tilt observed at the farthest point to that observed at the nearest point to the coast line amounts to 3 .5. In addition, each tidal component of crustal tilt generated by oceanic load is smaller than the tilt generated by seiche in Aburatsubo Bay.View full abstractDownload PDF (962K) -
-Estimated Error of Deduced Strain-Katsumi NAKANE, Yoichiro FUJII1982 Volume 28 Issue 2 Pages 82-85
Published: September 30, 1982
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSWe can obtain the displacement vector x with its variance-covariance matrix Σx after the net-adjustment of two surveys that are carried out for different epochs t' and t". These are given byx=X'-X" Σx=Σ'x+v"x, where X' and X" are co-ordinate vectors of the new and old positions of the triangulation stations, and and"x are variance-covariance matrixes of X' and X". The strain is calculated by the displacement vectors at the respective three triangulation stations. The strain vector u is expressed byu=A x, xt=(x1x2x3y1y2y3), where A is a coefficient matrix. The variance-covariance matrix of Σu is given by Σu=AΣxAt. Summary of the estimated strain error calculated from the second order triangulation survey is as follows;(1) Errors of dilatation and principal strain are in order of ±20×10-6 -or more, (2) Error of maximum shear strain is as large as ±20×10-6, (3) Error of principal axis is as large as ±20°. When the maximum shear strain is smaller than 20×10-6, the direction of the axis is unstableView full abstractDownload PDF (474K) -
Michio TAKADA, Tamotsu FURUZAWA, Shuzo TAKEMOTO, Kensuke ONOUE1982 Volume 28 Issue 2 Pages 86-97
Published: September 30, 1982
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSFor the purpose of finding out some clues for the earthquake prediction, continuous observations of crustal deformation with extensometers and tiltmeters at several stations have been carried out during about 20 years. Observational points are Oura, Donzurubo, Amagase and Iwakura, locating almost on a straight line in the SW-NE direction in the central part of the Kinki district. The ground-strains and -tilts were compared with seismic activities in the vicinity of each observatory. And it was found that the secular variations of the areal dilatations had the chara cteristic change in common to all stations, and that these changes moved with the velocity of about 30 km/year to the direction from SW to NE, that is, in order of Oura, Donzurubo, Amagase and Iwakura.View full abstractDownload PDF (1076K) -
Takeshi ENDO1982 Volume 28 Issue 2 Pages 98-110
Published: September 30, 1982
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSTidal gravity observations were made with a LaCoste and Romberg (G 34) gravimeter during 80-100 days at four stations in Central Japan ranging from latitude 35°N to 38°N. At the base station (Tokyo) observations were made twice, before and after the period of observations at other three stations, to check the reliability of the obtained tidal para meters. The tidal constants for different two epochs at the Tokyo station agree reasonab ly well. The result of the analysis shows that the tidal factor has a tendency to decrease systematically with a distance from the Pacific coast to Japan Sea coast. However, such a tendency, consistent with the regional distribution of effects of ocean tides, is almost eliminated by ocean tide corrections, by using TIRON et al . and PARKE-HENDERSHOTT models. The fluctuation of the observed phase lags are also reduced to some extent by the ocean tide corrections. The tidal factor obtained at an inland station (Yatsugatake) is 1-3% small relatively to those obtained at the other stations. This result may suggest the possibility of a regional anomaly of tidal factor. The lateral heterogeneity in the crust-mantle or the long-wavelength topography can be considered as a possible cause. Simultaneous tidal observations at many stations in Central Japan are necessary for confirming this regional anomaly.View full abstractDownload PDF (1494K)
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