All issues
Volume 23 (1977)
- Issue 4 Pages 213-
- Issue 3 Pages 135-
- Issue 2 Pages 57-
- Issue 1 Pages 1-
Volume 23, Issue 4
Displaying 1-7 of 7 articles from this issue
- |<
- <
- 1
- >
- >|
-
Gen-ichiro HORI1977 Volume 23 Issue 4 Pages 213-222
Published: March 25, 1978
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSNon-rigid effect on the rotation of the earth is studied by a mathematical model of resonance raised in the free nutation by an assumed forced oscillation of the moments and products of inertia of the earth. It is shown that the Euler period of the rigid earth shifts to the Chandler period if the assumed oscillation has an amplitude of 10-9C. In general, however, the Chandler period changes slowly about its mean value. Corresponding to this change, the radius of the polar motion changes too.View full abstractDownload PDF (631K) -
SHUZO TAKEMOTO1977 Volume 23 Issue 4 Pages 223-231
Published: March 25, 1978
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSIn order to measure the ground-strain with an accuracy of 1 part in 109, the superinvar bar extensometer with a laser interferometric device was developed. The fringe displacement in the interference pattern, together with the strain change, was converted photo-electrically by an image sensor consisting of a row of 64 photodiodes. The present resolution is one-thirtieth of the fringe displacement, corresponding to the strain change -of 2.5x10-10. Strain records obtained with this laser interferometric device (L) and with the con-ventional "roller" detecting device (R) for a period of 126 days were compared and the following relationships between them were found. R/ L≤0.5 for the range of relative displacement amplitude of 1-2μm, and R/L=1 for the range of relative displacemet amplitude larger than 4μm. Tidal strain amplitudes observed with the laser interferometric device were 39x 10-9 (M2) and 3.1x10-9(O1).View full abstractDownload PDF (1017K) -
Naomi FUJITA1977 Volume 23 Issue 4 Pages 232-238
Published: March 25, 1978
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSIn the western part of Japan, 1st order triangulations were carried out three different times by GSI. The horizontal displacement in the western part of Japan during the period from 1945-1955 to 1968-1972 is discussed by using the second and third set of geodetic data. In the horizontal displacement obtained under the condition of Συ=0 (Fig. 1), rotational movement is found in the Kui and Shikoku districts which is unusual. First, the accuracy of observation is examined. The distribution of observation error is shown in Fig. 3. The standard deviation of an angle with unit weight is shown in Table I. The accuracy of observation in the third geodetic survey is lower than those of the first and second ones. Second, the Monte Carlo Method is applied to the occurrence of observation error obeying to the Gaussian distribution. The systematic tendency is found here and there in the cumulative error (Fig. 4). It seems likely that the rotational movement appearing in Fig. 1 may be related to the apparent cumulative error. The latest horizontal displacement in the western part of Japan is shown in Fig. 6, assuming 13 fixed points. This assumption is the same as that of Fig. 5, which is con sidered as the co-seismic horizontal distribution of the Nankai Earthquake with M 8.2 of 1946. Fig. 6 clarifies as follows. 1) In the Kui Peninsula the horizontal displacements almost disappear. 2) In the Shikoku district the horizontal movement is about 1 m maximum in the same direction of Plate movement. It is noted that the horizontal displacement of No. 264 at Ashizuri Pt. is in almost the same direction during and after the Earthquake.View full abstractDownload PDF (575K) -
Yoichiro FUJII, Katsumi NAKANE1977 Volume 23 Issue 4 Pages 239-253
Published: March 25, 1978
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSThe second order triangulation stations that are located in the northeastern part of the Izu peninsula, Japan, were surveyed at four times in 1884, 1925/1926 1931, 1973 respectively, and the earth's horizontal strains are calculated from survey data for three epochs. Remarkable strain changes near the Oiso hills and the coastal line between Odawara and Atami are noticed in the figure in which maximum shear strains for the first epoch 1884-1925/1926 are shown. These strain changes that are associated with the 1923 Kanto earthquake can not be interpreted by the fault model of the earthquake given by ANDO (1974). The detected strain relief should be attributed to the reverse faulting off the Oiso hills and along the Nishi-sagami-bay fault. The strain relief associated with the 1930 Ito earthquake swarm and the Kita-izu earthquake are found in the strain figure for the second epoch 1925/1926-1931. An anomalous maximum strain accumulation amounting to 5 × 10-5 is detected near Atami in the strain figure for the third epoch. 1931/1973. This strain accumulation near Atami seems to originate from subduction of the Philippine Sea plate along the Nishi-sagami-bay fault as suggested by Ishibashi (1977). The results of strain analysis from survey data during 1931-1933/1934 show that some of detected strain accumulation originated from the creep dislocation at depth along the extension of the Nishi-sagami-by fault. Theref ere, the detected strain anomalies are nott always of a seismic nature that gives elastic rebound relating the subduction of the Philippine Sea plate. Finally, tectonic significances of the subduction zone bounded by the Sagami-bay fault and the Nishi-sagami-bay fault are emphasized. This boundary is nothing but the northern boundary of the Philippine Sea plate that is drifting to the direction N25°W at the present time, and the elastic or anelastic reverse f aultings along this boundary governn the seismo-tectonics in the south Kanto district.View full abstractDownload PDF (2273K) -
Katsumi NAKANE, Yoichiro FUJII1977 Volume 23 Issue 4 Pages 254-260
Published: March 25, 1978
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSThe second order triangulation had been performed in the South Kanto district during 1883-1885. The area around Tokyo Bay was resurveyed during 1899-1900. We do not know the reason why the resurvey was made in the area. The third order trianguration was performed in 1902 around the area of the west part of Tokyo Bay. We calculated preseismic horizontal strain from these observations during the period from 1884 to 1900 preceding the 1923 Kanto earthquake. The summary of the result is as follows. The minor principal axis of the strain is almost parallel to the Sagami Trough. The polarity of the strain axes reversed at the coseismic movement and returned to the preseismic one during postseismic movement. The preseismic strain velocity is much larger than the one in the steady state stage.View full abstractDownload PDF (703K) -
Izuo OZAWA1977 Volume 23 Issue 4 Pages 261-267
Published: March 25, 1978
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSNear the ground surface, components of the relative displacement, u', v' and w' on the crust are obtained by means of observations of three extensometers which are on these orthogonal directions, and four rotationmeters. For example, ∂u/∂x, ∂v/∂y and aw/az are observed by means of extensometers. Also ∂v/∂x, au/ay, ∂w/∂x (=-∂u/∂az) and ∂v/∂z (=-∂w/∂y) are observed by rotationmeters, ∂w/∂x and away are observed also by means rof tiltmeters, approximately. These observations have been done by using three orthogonal components of three extensometers (∂u/∂x, ∂v/∂y and ∂w/∂z), by using two rotationmeters (∂v/∂x and ∂u/∂y), and by using two horizontal pendulum type tiltmeters (∂w/∂x and ∂wl ∂y) in the old Osakayama Tunnel. These main strains, the maximum shear and three components of these rotational strains are then analysed every month. According to this analysis, the direction of these main strain has usually been in the prime vertical direction as well as those of the main stresses in most earthquakes in this district. The rotational direction has been to the east which agrees with the results of the analyses of the triangulations.View full abstractDownload PDF (489K) -
Naomi FUJITA1977 Volume 23 Issue 4 Pages 268-269
Published: March 25, 1978
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSDownload PDF (152K)
- |<
- <
- 1
- >
- >|