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Volume 22 (1976)
- Issue 4 Pages 201-
- Issue 3 Pages 139-
- Issue 2 Pages 65-
- Issue 1 Pages 1-
Volume 22, Issue 1
Displaying 1-8 of 8 articles from this issue
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Takeshi DAMBARA1976 Volume 22 Issue 1 Pages 1-9
Published: June 25, 1976
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSResurvey of the 3rd order triangulation in the Tanna area was carried out in 1973. This net is a part of area where the left-lateral fault of 2.-3 m displacements appeared at the time of the Kita-Izu earthquake (1930). The present survey used a method of trilatelation together with traversing by electronic distance measurements. Regardless of such technical methods, horizontal displacements during the period from 1933 to 1973 can be discussed. The past triangulation in Japan had no Laplace station. Besides, the concerned net is the 3rd order triangulation, so directly measured base lines are not involved. By these two reasons, displacement, which is calculated under assumptions of one fixed station and one fixed azimuth, usually shows pseudo rotation vector and pseudo convergent/ divergent vector. These pseudo signals can be successfully removed by applying a new method of signal coincidence. The corrected displacements show clear difference between east and west sides from the past fault line. The relative displacement is about 20 cm. At a glance, it may suggest continuation of movement along the slip surface of the fault. This idea, however, is denied by the fact of stable maintenance of the Tanna tunnel where displacement of 2.4 m appeared in 1930. Then, the horizontal displacements obtained at the present must be explained as follows: The crust of the east side of the fault is being displaced relatively to that of the west side. Accordingly, strain is accumulating in area along the past fault line. In order to obtain accumulated strain after the earthquake, some triangle must be chosen in which its vertex is located near the fault and both sides including the vertex angle are in perpendicular as long as possible with the fault line. The mean value of maximum shear strain is 3.7?105. The Yamakita area in the Kanagawa Prefecture can exactly be treated by the same way as in the Tanna area.View full abstractDownload PDF (856K) -
Takeshi DAMBARA1976 Volume 22 Issue 1 Pages 10-16
Published: June 25, 1976
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSA method of signal coincidence is applied to the first order triangulation net in the Chubu District. The old and new surveys were carried out in 18831897 and 19511960, respectively. The old survey involved 3 base-line surveys, while the new survey involved 1 base-line survey and 3 side-line measurements with an electronic distance measurement device. Although the new survey involved several Laplace stations, no astronomical observation was carried out in the old survey. So large scale factor s= Vr/R is unexpected in displacement vectors between the old and new surveys. But somewhat large rotation a=Vθ/R may be involved. These facts are clearly demonstrated in Fig. 3. After treatment of the method of signal coincidence, horizontal movements are ob tained, and their final result is shown in Fig. 6. It is interesting that large horizontal movements amounting to about 2 m with the direction of WNW in the Tokai area which is near to epicenters of huge earthquakes occurred in 1096, 1498, 1707 and 1854. Hori zontal strain is also calculated for the Chubu District.View full abstractDownload PDF (621K) -
Yukio HAGIWARA, Hirokazu TAJIMA, Sadakatu IZUTUYA, Mikio SATOMURA1976 Volume 22 Issue 1 Pages 17-22
Published: June 25, 1976
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSThe 1974 Izu Hanto-oki earthquake occurred with a right-lateral strike-slip motion of Irozaki fault inducing vertical and horizontal displacements of the peninsular crust. As compared the postseismic gravimetric results with the 1970 ones, gravity increase up to 4060 μgals was detected on the southeastern coast of Izu Peninsula by assuming no gravity change at BM 9402 on the northwestern coast. Possible causes of the gravity changes are presumed on the basis of geodetic results including the faulting motion. It is concluded that the gravimetric results reflect the earthquake-induced density increase plus the gradual peninsula-wide crustal deformation independent of the earthquake induction.View full abstractDownload PDF (838K) -
Jiro SEGAWA1976 Volume 22 Issue 1 Pages 23-39
Published: June 25, 1976
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSGravity data obtained by the author in 1972 using a LaCoste & Romberg Air-Sea Gravity Meter (S-32) are made public in this report. The author has also compiled a free-air gravity anomaly map in the Ryukyu Arc using the present data as well as those obtained by the US National Ocean Survey's ship "Oceanographer" in 1972 and those obtained by the Lamont-Doherty Geological Observatory.View full abstractDownload PDF (2581K) -
On Effects of Tunnel Excavation Executed in the Vicinity of an Observation Gallery on Strain RecordsAkira ADACHI1976 Volume 22 Issue 1 Pages 40-48
Published: June 25, 1976
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSStrain steps and secular strain changes were recorded by strainmeters during a period of tunnel excavation executed in the vicinity of an observation gallery. The strain steps are interpreted as rock deformations caused by shots for blasting a rock, not as instrumental instabilities, because they were recorded similarly by two strain meters installed in parallel to each other. All of the strain steps recorded were in the sense of ground extension, and this fact can be explained as the strain release produced by insertion of a horizontal cylindrical hole in a gravitating elastic body. Amplitude of the strain steps may be affected by inhomogeneities of rocks between shot points and the observation point. Secular strain changes seem to be connected with inelastic deformation of rocks around the tunnel, but precise explanation for the changes is not given in the present paper.View full abstractDownload PDF (981K) -
Masakazu OHTAKE1976 Volume 22 Issue 1 Pages 49-52
Published: June 25, 1976
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSGravity change (Δg) at the Matsushiro Firstorder Gravity Station during the Matsushiro earthquake swarm, 19651967, is thoroughly discussed based on revised data of altitude change (Δh). Newly constructed ΔhΔg diagram is not harmonious to Bouguer nor dilatancy gradient which were proposed by previous investigators. The best fit of observation data appears to correspond to Bouguer gradient for water. This finding supports the "water eruption" hypothesis of the Matsushiro earthquake swarm.View full abstractDownload PDF (427K) -
Yukio HAGIWARA1976 Volume 22 Issue 1 Pages 53-55
Published: June 25, 1976
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSDFT (Discrete Fourier Transform) procedure is applied to linear relation between gravity anomaly and the corresponding subsurface topography in comparison with the sin χ/χ method introduced by TOMODA and AKI.View full abstractDownload PDF (274K) -
[in Japanese], [in Japanese]1976 Volume 22 Issue 1 Pages 56-57
Published: June 25, 1976
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSDownload PDF (202K)
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