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Volume 19, Issue 4
Displaying 1-10 of 10 articles from this issue
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Masanori SAITO, Hitoshi TAKEUCHI, Naota KOBAYASHI1966 Volume 19 Issue 4 Pages 235-236
Published: March 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSPeriods of free oscillations of degree 2 are calculated for a moon model with a liquid core. It is shown that the period of torsional oscillation increases more rapidly with increasing core radius than that of spheroidal oscillation.View full abstractDownload PDF (165K) -
Distribution of Epicenters of Earthquakes in and near JapanMamoru KATSUMATA1966 Volume 19 Issue 4 Pages 237-245
Published: March 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSIn order to show the general feature of seismicity in and near Japan, epicenters off earthquakes have been plotted in the maps of Japanese islands.
1) The data in 15 years from 1951 to 1965 have been made use of.
2) The epicenters of earthquakes of different depths have been plotted on the different maps.
3) The magnitudes of earthquakes are shown in the maps by the size of epicenter marks. The magnitudes of earthquakes whose foci are deeper than 60km are determined with the method proposed by the present author.
4) The epicenters of earthquakes whose magnitudes are larger than 41/2 are plotted in the maps, but it should be mentioned that the earthquakes whose epicenters can be determined without omission by the J. M. A. are those whose magnitudes are larger than 52/1-53/4.
The important results are as follows:
1) The epicenters of very shallow earthquakes are equally distributed in and near Japan.
2) The seismic activities are most remarkable in the depths from 40 to 70km. Also it is easily seen that the most active zone is in the zonal area of Pacific Ocean side north from Kwanto district.
3) The epicenters of earthquakes of intermediate depth from 70 to 300km are rather widely distributed in and near Japan, but the two rather concentrated zones, one from the Kurile islands to Bonin islands and the other from Kyushu to the Ryukyu islands, are noticed.
4) The epicenters of earthquakes whose foci are deeper than 300km are distributed according to the wellknown belts, one crossing Japan transversely to Manchuria, the other extending from Manchuria across southern Sakhalin into the Sea of Okhotsk.View full abstractDownload PDF (658K) -
Kei TAKANO1966 Volume 19 Issue 4 Pages 246-254
Published: March 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSIn a previous paper (1963), Q of short period P waves was determined by a method based on two assumptions: 1) The value of Q is constant, at least, in the frequency range from 1 to 7 cps; 2) The type of spectrum near the focus is such that the amplitude of each component is inversely proportional to the frequency. It was shown that Q of short period P waves had large values of order of few thousands.
In the present paper, Q of short period S waves is determined from the records of distant earthquakes by the same method as that used for short period P waves. Its value is ranged from 400 to 2400. In each earthquake, it is smaller than Q of short period P waves for frequency range from 0.2 to 7 cps. For this frequency range, Q seems to be nearly constant for short period S waves.
It is pointed out that short period S waves are even more predominant in some cases than short period P waves obtained from earthquakes whose epicentral distances are shorter than 30 degrees.View full abstractDownload PDF (638K) -
Hitoshi TAKEUCHI, Masanori SAITO1966 Volume 19 Issue 4 Pages 255-260
Published: March 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe Haskell's method is very useful in studying the dispersion of surface waves in multilayered media in rectangular coordinates. It is, however, difficult to extend the method to spherical coordinates. Instead of exponential functions in rectangular coordinates, we must make use of spherical Bessel functions. This is one of the difficulty we meet in the extension. This difficulty may be avoided by using the constant matrix method proposed by Frazer and others. The most complicated part in applying the constant matrix method to the study of surface waves in spherical coordinates is to calculate characteristic exponents of the matrix in each step of the numerical integration. This calculation is made in the present paper and explicit results are shown both for torsional and spheroidal (with and without gravity) oscillations of the earth.View full abstractDownload PDF (439K) -
Hitoshi TAKEUCHI, Masanori SAITO1966 Volume 19 Issue 4 Pages 261-271
Published: March 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSBy using energy integrals, we can reduce the excitation problems in layered media to forms in which we need no additional calculation than eigen frequency, eigen functions and kinetic energy integrals for each wave number and excitation spectrums at the origin.View full abstractDownload PDF (614K) -
Yasuo SHIMAZU, Jun IRIYAMA1966 Volume 19 Issue 4 Pages 272-277
Published: March 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSUnsteady mantle convection is studied as a continuation of previous papers. The size of the convection cell is assumed to be 6, 000×3, 000km. Numerical calculations are carried out until a reversal of the initial temperature distribution is realized. The convection is shown to be able to pass through the C-layer (olivine-spinel transition) without any difficulty.
Secular variations in isotherm, velocity, stress and heat flow through the Moho are obtained for various boundary conditions (free and rigid surface, free and rigid sides). For ν=1024cm2/sec the horizontal speed at the surface reaches 3cm/year in the case of stress free. When the surface is rigid the maximum shear stress reaches 1.2kb. The life of convection is an order of 1, 000 million years.View full abstractDownload PDF (435K) -
Yasuo SATO1966 Volume 19 Issue 4 Pages 278-280
Published: March 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (312K) -
Masaji ICHIKAWA1966 Volume 19 Issue 4 Pages 280-282
Published: March 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (271K) -
Ikuei MURAMATU1966 Volume 19 Issue 4 Pages 282-285
Published: March 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (244K) -
Otozo HAMAMATSU1966 Volume 19 Issue 4 Pages 286-305
Published: March 25, 1967
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSHistorical records of seismographs used for routine observations at stations of J. M. A. network are arranged in tabular form.
Main table includes: 1) Name of station, 2) Date of foundation and closing (or movement) of each station, 3) Date of starting and ending observations for each kind of seismograph, 4) Longitude, latitude and height of stations where observations have been stopped by various reasons. Auxiliary table showing instrumental constant characterizing various kinds of seismographs is also prepared.View full abstractDownload PDF (1649K)
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