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Volume 8, Issue 1
Displaying 1-9 of 9 articles from this issue
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Toshi ASADA1955 Volume 8 Issue 1 Pages 1-7
Published: July 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSIt is well known that big earthquakes are always accompanied by many aftershocks, but aftershocks are not registered after small ones. However, strictly speaking, we know little about the boundary in magnitude between the earthquakes accompanied by aftershocks and the ones not accompanied by them. In this paper the present author studied this problem. The materials used are the data of the earthquakes occurring in Kanto District, JAPAN. The results are shown in the following table.View full abstractDownload PDF (567K) -
Ryosuke SATO1955 Volume 8 Issue 1 Pages 8-22
Published: July 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSAs the wave-length of the seismic wave is very large compared with the roughness of corrugated surface for most cases, it is generally negligible. But if the period of incident seismic wave is very short, we cannot overlook the effect of the roughness.
Lord Rayleigh had studied the theory of reflection and refraction of sound in his ‘The Theory of Sound’, where plane waves were supposed to be incident perpendicularly upon a regularly corrugated boundary, whose form was limited to simple trigonometrical functions. After that he extended the above theory and discussed it more in detail in ‘Pro. Roy. Soc., A, Vol. LXXIX. pp. 399-416, 1907’.
We investigated in this paper, after Rayleigh, the theory of reflection of elastic waves on corrugated free surface, supposing the depth of the corrugations is small in comparison with the length of the waves.
The refleected waves are composed of regularly reflected waves and various spectra. If the wave-length of corrugation is small compared with that of distortional wave, the waves reflected as bodily waves are only regularly reflected waves; besides, the waves, whose amplitudes diminish as z increases, are propagated in both directions of x with the velocity depending upon the wave-length of corrugated surface and the angle of incidence. When the wave-length of the corrugations becomes large, the spectra of reflected bodily waves gain in number but so long as the wave-length of the corrugations is finite, the above waves are propagated along the surface.View full abstractDownload PDF (1112K) -
Kyozi TAZIME1955 Volume 8 Issue 1 Pages 23-33
Published: July 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSGeneral expression of the coupling-effect was given. Several previous papers were discussed, regarding to that expression. Our useful expression was developed to more practical schemata, Fig. 2-Fig. 9. The conclusions were given from those calculations: (1) In order to neglect the coupling-effect, the damping factors, especially those due to A1 or A2, are smaller the better, on the contrary the ratio of the natural periods proper to the respectives are larger the better. (2) From practical view point, it will be difficult to neglect the coupling-effect in the case σ≈1. (3) These considerations may be applied to transient phenomena, including the observation of free oscillation of a pendulum.
The dynamical properties of our system may be greately influenced by the small changes of the constants proper to the equipments. Therefore, I believe, the coupling-effect must be considered also in the case of comparing the relative wave forms by means of respective observational systems, when the coupling effect cannot be neglected.View full abstractDownload PDF (1072K) -
Sadao MIYAMOTO1955 Volume 8 Issue 1 Pages 34-37
Published: July 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe present nomograph for estimation of epicenter is made without considering Conrad layer and Mohorovicic layer.
The writer made two new nomographs taking into account Conrad layer and Mohorovicic layer.
Epicenter of Fukui Earthquake can be simply and exactly estimated as λ=136°17.′1 φ=36°7.′1 by new nomographs.
Also the Focal depth is very simply estimated to be 35km.
Therefore, the present nomographs must be improved.View full abstractDownload PDF (314K) -
Michiyasu SHIMA1955 Volume 8 Issue 1 Pages 38-44
Published: July 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSOn the assumption that the mantle is composed of the ionic crystals, the distribution of the ratio of bulkmodulus k to density ρ and the pressure p is investigated by means of the atomic theory to reveal the change occurring between the layers B (33km-413km) and D (1000km-2898km). It is found that, if this change were the polymorphic transition from low pressure phase to the higher one, the decrease of the gradient of k/ρ would occur between B and D. Then, this may be of the chemical composition. If so, the dissociation energy and the reduced density ρ0 increase and the inverse power n of the potential between the atoms hardly change there.View full abstractDownload PDF (469K) -
Izuo OZAWA1955 Volume 8 Issue 1 Pages 45-47
Published: July 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSIt was almost impossible to eliminate the all meteorological effects on crustal deformation from the observed curves of our highly sensitive extensometer. The seasonal differences of range of fluctuations of observed linear strain-variations of the earth-crust at Osakayama (Otsu) Observatory computed, in this paper are confined in the small range as compared with anomalies of strains of the ground accompanied by strong earthquakes.View full abstractDownload PDF (310K) -
Ituo TAMAKI1955 Volume 8 Issue 1 Pages 48-54
Published: July 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThis is the 3rd paper on the study of the structure of the earth crust of Japan. In this paper, the author discussed the anomalies of incident times of P-waves from deepfocus earthquakes. Using the travel time curves of 41 remarkable deep earthquakes occurred in 1935-4953 (their epicenters are plotted in Figure 1), the mean values of the deviations from the normal curves at easy observations (ΔTobs.) are obtained. Corresponding with these observed anomalies, the values of the expected anomalies (ΔTcal.) from the author's model for the structure of the crust of Japan are calculated. The values of this two sorts of anomalies, observed and calculated, are shown in Table 1. The geographical distributions of the anomalies are shown in Figure 2 and 3. Comparing with two maps, we can find that the distributions of ΔTobs. agree well with that of ΔTcal. Figure 4 is the scatter diagram for those two sorts of values. The figure indicates that there is the linear colleration between two values. In consequence, the author assert that the observed deviations of the incident time of deep focus earthquakes are caused by the irregularities of the structure of upper crust, and especially, the large parts of the values of them are to be explained by the author's model for the crust of Japan.View full abstractDownload PDF (608K) -
Saburo KOMURA1955 Volume 8 Issue 1 Pages 55-56
Published: July 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (178K) -
Keiiti AKI1955 Volume 8 Issue 1 Pages 56-58
Published: July 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (1811K)
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