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Volume 19, Issue 3
Displaying 1-6 of 6 articles from this issue
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Mitsuhiko SHIMADA1966 Volume 19 Issue 3 Pages 167-175
Published: December 25, 1966
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSMelting of natural olivine basalt has been measured at pressures up to 35 kilobars by using the differential thermal analysis with the quenching method.
Three melting relations of basalt are shown, classified according to the water content in the samples: the total pressure is assumed equal to the water pressure; the samples contain 0.98wt% of water (no adsorbed water); 1.60wt% of water. The last two cases have been found to correspond to those with the water pressure less than the total pressure.
These melting relations have been compared with the temperature distribution in the upper mantle. And the results suggest the existence of the molten zone in the upper mantle, assuming the presence of basaltic composition and water (even to the extent of water of crystallization).View full abstractDownload PDF (704K) -
Yoshiteru KONO1966 Volume 19 Issue 3 Pages 176-186
Published: December 25, 1966
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSReferring to the studies by Shimazu and Kono (1963, '64), two dimensional stress distributions within the unsteady convection cell and their secular variations are calculated. The results obtained are as follows: (1) The stress distribution is strongly affected by the type of boundary conditions at the upper and lower surface, i. e. fixed (rigid) or free. When the upper surface (Moho) is stress free, the stress is concentrated at the rising and sinking areas. When the upper surface is rigid, it is concentrated in the middle of the rising and sinking areas. (2) The patterns and magnitudes of stress within the cell are not significantly varied with time.
Based upon the stress distributions thus obtained, the distribution of the deep focus earthquakes and the elastic anisotropy of the upper mantle are discussed.
Furthermore, a possibility of stirring of the mantle by convection current is checked. It is concluded that the upper mantle is nearly completely stirred during the one cycle of the convection.View full abstractDownload PDF (972K) -
Minoru HORI, Hideteru MATUMOTO, Keiichi AKI1966 Volume 19 Issue 3 Pages 187-199
Published: December 25, 1966
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSAfter the Alaska Earthquake of March 28, 1964, we set up a temporary array station near Lawing, Kenai Peninsula, Alaska, about 125km south-west of the epicenter of main shock. The observation was carried out from May 19 to June 7, 1964.
Using the tripartite method, we determined the epicenters and focal depths for 797 shocks in the 20 days.
This paper described briefly the method and result obtained by the observation. A complete list of epicenters, and detailed discussions on the result will be published in a pubilication of the U. S. Coast and Geodetic Survey.View full abstractDownload PDF (1709K) -
Yoichiro FUJII1966 Volume 19 Issue 3 Pages 200-216
Published: December 25, 1966
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDuring Jun. 1964 and Mar. 1956, the Geographical Survey Institute carried out the resurvey of the gravity in the shock area of the Niigata Earthquake, 16 Jun. 1964 immediately after its occurrence. By using the results of these works, we can discuss the possibility of the gravity change in this area. Also summarizing the results of all the other re-surveys in Niigata Plain we can study the change in this plain. There are many level-lines where the re-survey of gravity was made at various chances.
In the study of gravity change, it is the main purpose to detect the change in gravity caused by the change in density of the underground mass. So we adopt the method of comparing the old with the new Bouguer anomaly value calculated by the G. S. I. system where the vertical change in gravity is assumed to be 0.3086mgal/m, the density of the mass above sea level is 2.67, and no topographic correction is applied.
By this comparison, the following two facts can be accepted;
(1) Along the level line from B. M. 6519 to B. M. 6493 that runs near the sea shore of Honshu opposite to Awashima island, it was found that the wave-form change of Bouguer anomaly during 1954 and 1964 with the amplitude of 0.25mgal and the half wave length of 52km.
(2) In the Niigata Plain along the level line from B. M. 6475 to B. M. 4430, also there was found the decrease of Bouguer anomaly during 1954 and 1964 with the amplitude of 0.25mgal and the half wave length of 50km.
In order to discuss the meaning of these phenomena, we assume the distribution of the observed change in gravity at earth surface as 0.25mgal·sinπ/52km·xkm in the case of (1). Then the corresponding mass distribution with 0.25gr/cm3 change in density is proved to be 108m·sinπ/52km·xkm at depth of 25km that is the mean depth of the after shocks of Niigata Earthquake. The corresponding change of vertical gradient of gravity is 1.5×10-5mgal/m·sinπ/52km·xkm.
In the case of (2), as the thickness of the deposit of low density that is presumed to be a cause of the negative Bouguer anomaly in Niigata Plain is 1800m at its maximum, we try to calculate how much growth of this deposit can explain the change in gravity. The observed distribution of gravity change is 0.25mgal·sinπ/50km·xkm, then the corresponding growth of the thickness of the deposit is 8.9m·sinπ/50km·xkm during 10 years. This value is too great by ten times as compared with the rate of crustal deformation obtained by the first order leveling.View full abstractDownload PDF (1264K) -
Izuo OZAWA1966 Volume 19 Issue 3 Pages 217-225
Published: December 25, 1966
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe continuous records of the crustal deformations have been got with extensometers, horizontal pendulum type tiltmeters and water tube tiltmeter at Osakayama Observatory before and after the earthquake near the city of Kyoto. The seismic intensity was 3 (rather strong), and its epicentral distance was 12.7km.
In this paper, using the abrupt changes of the strains in the time of the earthquake, we calculate the radius of the earthquake volume, the total change of the elastic energy and the seismic magnitude. The elastic afterworking of the earthquake region has been observed with the high-sensitive and high speed's recording extensometers. According to the record, the relaxation time of the afterworking is 57 minutes, and then the solid viscosity in the seismic area is esteemed as 1014 c. g. s..View full abstractDownload PDF (1418K) -
Tokuji UTSU1966 Volume 19 Issue 3 Pages 226-227
Published: December 25, 1966
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (284K)
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