Zisin (Journal of the Seismological Society of Japan. 2nd ser.)

Surface Waves of Short Periods

Teshikaga Earthquakes in 1965

Toshikatsu YOSHII

1969 Volume 22 Issue 2 Pages 83-93
Published: August 30, 1969
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.22.2_83

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Surface waves of short periods were finely found on the records of three Teshikaga earthquakes in 1965. The observation point was Kushiro in Hokkaido and the seismometer used was Type 59 of J. M. A.. The magnitudes of these earthquakes were about 5 and the epicentral distances were between 50 and 60km. The EW-component of the seismometer recorded Love waves and the NS- and the vertical components recorded Rayleigh waves, because the direction propagated by these surface waves was nearly north to south. Three modes, M₁₁, M₁₂ and Love were identified on the records and group velocities of them were obtained from these records. Only three models of the crustal structure are given in the present paper, though much more models were examined numerically. One of the successful models, HOK-5 B, has the sedimentary layer whose thickness is 2.25km.

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Model Experiments on Dispersive Rayleigh Waves Generated from a Sinusoidal Source of a Finite Duration in Case of a Sloping Interface

Mitsuo MOTOYAMA

1969 Volume 22 Issue 2 Pages 94-103
Published: August 30, 1969
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.22.2_94

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Experiments were carried out with two dimensional models which had various slope angles. Period of wave groups were changed from 10μs to 40μs. Three wave groups were distinctly observed. However, propagations of these wave groups were so complicated that dispersion curves could not be decided from the records observed.
Using the theoretical dispersion curves for dispersive Rayleigh waves in case of parallel layers, group velocities at any distance from the vertex of the sloping layer were obtained. Then, theoretical travel times were calculated for each wave group. The travel time of the most distinct wave group observed corresponds well to the theoretical time-distance curve of M₁₁. The other wave group may correspond to PL₂₁ near the vertex and to M₂₁ far from the vertex. Another is only refracted S waves, being P waves scarcely observed.

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Process in the Source Region for a Great Earthquake

The Tokachi-Oki Earthquake, 1968 and the Etorofu-Oki Earthquake, 1963

Tomeo NAGAMUNE

1969 Volume 22 Issue 2 Pages 104-114
Published: August 30, 1969
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.22.2_104

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On the strong motion seismograms at stations in Hokkaido and northern Honshu for the Tokachi-Oki Earthquake of May 16, 1968, remarkable waves with large amplitude are recorded at about 20-50 seconds after the S phases. The origin time and the hypocentral coordinates of this earthquake are given by JMA as follows; 00^h48^m53.0^s (GMT), 40°44′N, 143°35′E, H=0km.
By mean of the travel time analysis, it is found that these waves can be explained as the S wave radiated at the other place from the hypocenter of the main shock. The time and coordinates of the wave origin estimated by the application of Geiger's method are as follows; 00^h49^m38.3^s±1.3^s(GMT), 40°35′±00′N, 142°20′±00′E, H=0km.
From the strong motion seismogram obtained at Urakawa, Hokkaido, for the Etorofu-Oki Earthquake of Oct. 13, 1963, it is also suggested that the large energy was released at the other place from the origin of the main shock, even though such unique solutions for the time and the coordinates of the origin can not be estimated as above example.

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Daily Variation in the Temperature of the Cytherean Atmosphere

Tatsuo URABE

1969 Volume 22 Issue 2 Pages 115-120
Published: August 30, 1969
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.22.2_115

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Daily variation in the temperature of the cytherean atmosphere is discussed, based upon the radiation equilibrium condition. A coupling of two systems of day side and night side is the main interest.
According to the rotation of the planet, energy influx from the sun varies sinusoidally with time. However, variations in the radiation equilibrium temperature are not always sinusoidal, and a discontinuous jump at 350°K and 250°K is expected.
Wind of hot gas from the day side to the night side occurs continuously, and a temperature rise of 30°K is realized at the night side.

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Surface Heat Flow and Thermal State at the Japanese Islands area

Yasuo SHIMAZU, Yoshiteru KONO

1969 Volume 22 Issue 2 Pages 121-130
Published: August 30, 1969
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.22.2_121

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Surface heat flow is observed fairly well at the Japanese Islands area. It is our purpose to utilize the observed heat flow to estimate the thermal condition of the mantle.
Two-dimensional heat transfer equation of composite media is solved numerically. The equation is composed of several terms: conductive transport, convective transport, radiogenic heat generation, and metamorphic heat absorption. The boundary conditions are as follows; surface temperature is always equal to zero, and the heat flow at the bottom of the region is kept constant at 0.4×10^-6cal/cm²·sec. Crustal structure of the Japanese Islands area is referred from the recent seismological works. The region is devided into square grids. The medium number and the convective vector are specified by two digits for each grid point. Two digits forms a two-dimensional matrix, i. e. Medium Map. Therefore, the Medium Map represents both the crustal structure and the convective current pattern. The convective current is assumed to be stationary where both the current pattern and the velocity are presumed a priori.
Several thermal model of the Japanese Islands are discussed and it is concluded that the observed heat flow pattern is explained by the following model: upward mantle convection or large magma reservoir exists under the Japan Sea and no mantle convection or low temperature mantle convection exists under the Pacific Ocean side of the Japanese Islands.

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Energy Release of Earthquakes in the Vicinity of Kyoto (1)

Kennosuke OKANO

1969 Volume 22 Issue 2 Pages 131-135
Published: August 30, 1969
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.22.2_131

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The magnitude-frequency relation of micro-earthquakes occurring in the vicinity of Kyoto is extraporated to higher magnitudes to obtain the time interval at which one earthquake with arbitrary magnitude or greater is to be expected. The time interval thus obtained is comparable to the recurrence time of destructive earthquakes in the historical records.

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A Derivation of Ishimoto-Iida's Formula for the Frequency Distribution of Earthquakes from a Deformation-Fracture Relation

Shozaburo NAGUMO

1969 Volume 22 Issue 2 Pages 136-143
Published: August 30, 1969
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.22.2_136

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It is shown that Ishimoto-Iida's formula, n(a)da=ka^-mda, for the frequency distribution of earthquakes with respect to the maximum amplitude of earthquake motion at a certain observation station is derived from a deformation-fracture relation.
The number of earthquakes is assumed, as a deformation-fructure relation, to be proportional to the curvature of the plastic deformation of the medium. The frequency distribution of earthquakes with respect to the amplitude of earthquake motion, n(a)da, is assumed to be proportional to the distribution of the earthquakes with respect to the wave number k of the plastic deformation, n(k)dk.
Assuming further that the amplitude of earthquake motion is inversely proportional to the wave number of plastic deformation, which is a kind of the radiation relation, n(k)dk is transformed to n(a)da. Thus, n(a)da is derived from the plastic deformation of the medium.
The power function representation of n(a)da=ka^-mda of Ishimoto-Iida's formula is due to the power function representation for the spectrum of plastic deformation of the medium. The coefficient m indicates the sharpness of the spectrum of the deformation.
It is discussed that Ishimoto-Iida's formula is not a probability distribution of earthquake occurrence, but a causual physical law between the plastic deformation and the number of earthquakes.

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A Pre-Amplifier for Observation of Microearthquakes

Yoshimitsu OKADA

1969 Volume 22 Issue 2 Pages 144-145
Published: August 30, 1969
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.22.2_144

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Not Expensive Portable Data Recorders

Takeo MORIYA

1969 Volume 22 Issue 2 Pages 146-147
Published: August 30, 1969
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.22.2_146

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Geophysical Phenomena in the Old Testament

4. Ezekiel-Malachi

Ikuko OZAKI, Yasuo SATÔ

1969 Volume 22 Issue 2 Pages 148-150
Published: August 30, 1969
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.22.2_148

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Why is there no Core in the Moon?

Hitoshi TAKEUCHI

1969 Volume 22 Issue 2 Pages 150-151
Published: August 30, 1969
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.22.2_150

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