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Volume 21 (1975)
- Issue 4 Pages 179-
- Issue 3 Pages 131-
- Issue 2 Pages 75-
- Issue 1 Pages 1-
Volume 21, Issue 1
Displaying 1-6 of 6 articles from this issue
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Fumiaki KIMATA, Ryuichi SIHCHI1975 Volume 21 Issue 1 Pages 1-5
Published: July 25, 1975
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSTo verify continuous record of the ground tilt, in the vicinity of the Inuyama Crustal Movement Observatory, an about 30 km long leveling route consisting of 29 bench marks has been set up in 1967. The first survey was carried out in March 1968. Since six bench marks which belong to the Geographical Survey Institute were supplied along this route in 1969, a precise leveling has been continued under the project of the Institute every other year, namely, November 1969, March 1972 and March 1974. In the present 6 year's survey other period, vertical movement inclining to WNW or Wdirection with a tilt rate of 0.2-0.4×10-6 rad/year is found around Inuyama. A fairly good coincidence can be noticed between this vertical change and continuous record of the ground tilt observed with a water tube tiltmeter; not only in the secular change (0.5×10-6 rad/year to N40°W on an average) but also in the time variation of tilt rate. This movement is also in accordance with the vertical change of Chubu District in 1951-1967: 0.25×10-6 rad/year to WNW near Inuyama. During the survey period from 1929 to 1951, subsidence of the Nobi Plain which may be originated from the Quaternary tectonic movement has been observed, consequently tilting to WSW with about 0.5?10-6 rad/year at the neighbourhood of Inuyama. The present result is also concordant with this vertical movement.View full abstractDownload PDF (558K) -
Ichiro NAKAGAWA, Mikio SATOMURA, Makoto OZEKI, Hironori TSUKAMOTO1975 Volume 21 Issue 1 Pages 6-15
Published: July 25, 1975
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSContinuous observations of the earth tides are being carried out with an Askania gravimeter Gs-15 (No. 217), under an excellent condition, at Kyoto since June 1972. Data obtained for the first two years (June 1972-May 1974) were analyzed by Lecolazet's, Venedikov's and Fourier transform methods. These three different methods of analysis gave almost the same results so far as the main constituents of tides, and Kl constituent showed a remarkably seasonal variation in both tidal factor of gravity and phase lag. The data were also analyzed by the maximum entropy method, which was recently introduced by J. P. BURG in the field of geophysical studies and showed a highly resolving power, in order to get a fine spectral structure of the earth tides in the vicinity of terdiurnal and quarter-diurnal tides. The M3, S3, 2MK and MK constituents were clearly detected by the present analysis.View full abstractDownload PDF (1046K) -
Yukio HAGIWARA1975 Volume 21 Issue 1 Pages 16-18
Published: July 25, 1975
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSBouguer correction for the spherical shell with a thickness of h and a density of ρ is 4πIGρh (G is Newton's gravitational constant), which is twice larger than the conventional Bouguer correction for the infinite slab. Bouguer correction for the shell restricted to a spherical cap is formulated, and then the radius of the spherical cap, the gravitational attraction of which is equal to that of the infinite slab, is estimated.View full abstractDownload PDF (315K) -
Naomi FUJITA1975 Volume 21 Issue 1 Pages 19-21
Published: July 25, 1975
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSThe shear strain in rock fracture is derived using the Coulomb-Navier's theory, which is expressed by the following equations:
|τ|=S0-μσ
T0=2S0/√μ2+1+μ
C0=2S0/√μ2+1-μ
where
π: shear stress
σ: normal stress
μ: coefficient of internal fraction
S0 : shear strength
T0 : tensile strength
C0 : compressive strength
Between the shear strain γ and the normal strain ε the next relation holds for isotropic materials,
|γ|/2=S0′-με
where
S0′=1/2G(S0-μλλ)
λ=ε1+ε2+ε3
and
λ, G : Lame's parameters The strain quantities T0′ and C0′ corresponding to the tensile and compressive strengths, are expressed as follows :
T0′=2(γ+G)/G(3γ+2G) (√;μ2+1-μ)S0
C0=-2(γ+G)/G(3γ+2G) (√;μ2+1+μ)S0
The quantities of S0′, T0′ and C0′ are in order of 10-4 under suitable assumptions. It is in harmony with strain quantities obtained by the geodetic surveys before and after earthquakes.
These equations are represented by the Mohr's circle diagram in Fig. 2. The Mohr's circle moves depending on (ε1+ε3)/2 and the position of S0' depending on Δ=ε1+ε2+ε3. Accordingly, the state in which the dilatation is larger, is nearer to the rock fracture, even if the quantity of (ε1-ε3) takes the same value.
There is a strong correlation between the anomalous dilatation of the rhombus base lines at Mitaka, Tokyo and the occurrence of earthquakes of intensity more than V (JMA) at Tokyo. It leads him to suggest the relation between dilatation and fracture of the earth's crust.View full abstractDownload PDF (356K) -
Yukio HAGIWARA1975 Volume 21 Issue 1 Pages 22-25
Published: July 25, 1975
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSThe first correction term in the series solution of the geodetic boundary-value problem given by Molodenskii et al., is known under the popular name of "Molodenskii's G1". The term is also approximately derived from the vertical gradient of gravity anomaly. The physical meaning of G1 is sufficiently explained in the derivation method based on the spherical harmonic series representation.View full abstractDownload PDF (494K) -
PREPARED FOR THE XVI GENERAL ASSEMBLY GRENOBLE, FRANCE AUGUST 25-SEPTEMBER 6, 19751975 Volume 21 Issue 1 Pages 37-73
Published: July 25, 1975
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSThe fundamental framework of triangulation net was established for the whole land of Japan until 1913. It consists of 330 principal first order, 620 supplemental first order, about 5, 000 second order and about 33, 000 third order stations . Since then, local revision surveys have been carried out for many areas disturbed by destructive earthquakes . Fourth order triangulation was started in 1951 to serve mainly for cadastral survey and more than 37, 000 stations have been established in flat areas . Recently, about 2, 000 fourth order stations have been increasing every year . Revision survey for the entire network of the principal first order stations was started in 1947 in order to detect the crustal deformation as well as to revise the network and was completed in 1967. Then the third revision survey of the same network was continued and covered about one third of the whole network, but it was replaced by the “Precise Geodetic Net” project in 1973 as described below. Through results of the revision survey of the principal first order triangulation, the followings were obtained as the concluding remarks: 1) Crustal movements accompanied with earthquakes are very large in many parts of the land of the country. 2) As the result, of course, the coordinates of triangulation stations of the second or lower order, which were determined until 1913 and have still been used, have not always maintained the accuracy required for practical purpose. 3) Informations on the horizontal movement of the crust obtained from repetition of the triangulation are very useful for predicting the occurrence of huge earthquakes . 4) The principal first order triangulation net is too rough to know geodetically the precursors of destructive earthquakes even over magnitude 7. The survey of the lower order triangulation stations should repeatedly be carried out.View full abstractDownload PDF (52971K)
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