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Volume 5 (1957)
- Issue 2 Pages 69-
- Issue 1 Pages 1-
Volume 5, Issue 1
Displaying 1-8 of 8 articles from this issue
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Chuji TSUBOI1957 Volume 5 Issue 1 Pages 1-7
Published: 1957
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSBy using the newly deduced formula:
M=1.73logΔ+logA-0.83,
where M is the magnitude of an earthquake, and A is the maxium ground amplitude measured in micron at the epicentral distance Δ measured in km., the magnitudes of 1025 earthquakes which took place from 1931 through 1955 in and near Japan have been determined.
The mean annual number N of earthquakes according to the magnitude has been found to be expressed by
logN=-1.08+0.72(8-M),
for ΔM=0.1.
The mean rate of energy release by earthquakes in and near Japan has been estimated to be 1.5×103 ergs/cm2 year or 0.1×10-6 calory/cm2 sec.
As a whole, Japanese area is contributing well over 10% to the total seismicity of the world.View full abstractDownload PDF (511K) -
IZUO OZAWA1957 Volume 5 Issue 1 Pages 9-13
Published: 1957
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSObservations of tidal strain components of the earth's surface by means of extensometers were initiated by K. SASSA and the value of constant l, usually called SHIDA'S number, was obtained seperately from other constants h and k.
Observations of tidal strain components in three horizontal, one vertical and two diagonal directions are made at Osakayama Observatory. Using the observed values, horizontal areal strain, vertical strain and cubical dilatation are obtained, and the numerical values of h-3l, υ and C=υ+2h-6l are caluculated therefrom.View full abstractDownload PDF (390K) -
Shoshichiro KATO1957 Volume 5 Issue 1 Pages 15-24
Published: 1957
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSIn connection with the self-exciting dynamo problem, we study here time characteristics of magneto-hydrodynamical dynamos driven by fluid motions of magnitudes larger or smaller than those for stationary dynamos. For a given fluid velocity, there are infinite numbers of dynamos of different time characteristics. The fundamental dynamo (P1 solution in section 4) is developing or decaying according as the fluid velocity is larger or smaller than that for the stationary dynamo. There are also dynamos having quasi-periodical time characteristics. This periodical dynamo may be useful as a model for magnetic variable stars.View full abstractDownload PDF (768K) -
Naota KOBAYASHI, Hitoshi TAKEUCHI1957 Volume 5 Issue 1 Pages 25-32
Published: 1957
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSWave generations from line sources within the ground are studied. For a compressional origin of step function type in time, we calculate displacements at several points within the ground. In contrast to the surface displacement, we have, deep in the ground, three distinct pulses corresponding to the direct P, reflected P and S phases and no displacement corresponding to the RAYLEIGH wave.
Next, we calculate profiles of surface displacements for an impulsive compressional origin. The importance of surface reflections in generating long waves is shown.View full abstractDownload PDF (523K) -
Akira KUBOTERA1957 Volume 5 Issue 1 Pages 33-41
Published: 1957
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSCharacteristics of ground motions caused by small dynamite charges were studied. Seismometers were set up at various depths within bore-holes, and varying the depth of shot-hole, the explosive waves were recorded.
In this experiment, surface waves which could be considered as RAYLEIGH and SEZAWA waves were observed.
The characteristics of these waves are as follows.
RAYLEIGH wave:
The wave velocity is 60m/sec.
The period of motion is about 0.22sec.
The amplitude decreases exponentially with depth.
SEZAWA wave:
The wave velocity is 500m/sec.
The period of motion is about 0.1-0.08sec.
As to the vibration mode, there is one node in the upper layer.
These results are in good agreement with those predicted by the theories of RAYLEIGH and SEZAWA waves.View full abstractDownload PDF (1063K) -
LOVE-waves in Doubly Stratified Layers.KYOZI TAZIME1957 Volume 5 Issue 1 Pages 43-50
Published: 1957
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSThe period characteristics of the amplitude function of Love-waves were obtained by the use of the dispersion curves. The quarter wave-length law may be approximated by the period at the AIRY phase, but it can be better approximated by the period at the phase corresponding to the maximum of the amplitude function. These approximations, moreover, become respectively all the better with the increase of the rigidity ratio between superficial and lower strata. Differences between the maximum of the amplitude function and the maximum amplitude are also considered.View full abstractDownload PDF (577K) -
Kyozi TAZIME1957 Volume 5 Issue 1 Pages 51-59
Published: 1957
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSVariations of periods in superficial seismic waves were observed with various charge amounts. Those seismic waves were considered to be the zeroth and the first orders of RAYLEIGH and SEZAWA-waves respectively, due to the superficial layer in the experimental ground. Each period was found to have its own asymptotic value which was seen to satisfy the quarter wave-length law discussed previously by the present author. Frequency characteristics at the origin of seismic waves were also considered.View full abstractDownload PDF (1608K) -
Daisuke SHIMOZURU1957 Volume 5 Issue 1 Pages 61-67
Published: 1957
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSFor the purpose of investigating elastic properties of rocks at the melting point, the velocity of ultrasonic dilatational wave in polycrystalline sodium was measured from room temperatures up to its melting point. Very marked drops in elastic moduli with the corresponding decrease in the velocity were observed as the melting point is approached. The marked drop in the velocity near the melting point was compared with the order-disorder transition phenomena of a metal alloy. The nature of the core-mantle boundary (Bullen's region D") was discussed from such experimental evidences.View full abstractDownload PDF (610K)
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