Journal of Physics of the Earth

Is The Layer C (413-1000km) Inhomogeneous?

Haruo MIKI

1955 Volume 3 Issue 1 Pages 1-6
Published: 1955
Released on J-STAGE: April 30, 2009

DOIhttps://doi.org/10.4294/jpe1952.3.1

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There are opinions that the part of the earth's mantle is not homogeneous. 1-g^-1dφ/dr which was first introduced by SULLEN (1949), the calculation of velocities of seimic waves (BIRCH, 1939) and the density distribution based on WILLIAMSON-ADAMS-BULLEN'S method (BIRCH, 1954) have been thought as the evidences to show that these opinions are valid. The method developed in this paper shows that the density distribution can be derived without the assumption of hydrostatic equilibrium within the earth's mantle. The results obtained in the present paper show that the abnormal characters of the layer C (413-1000km) can be explained by the non-hydrostatic equilibrium state of the layer instead of its inhomogeneity.

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Wave Generations from Line Sources within the Ground.

Hitoshi AKEUCHI, Naota KOBAYASHI

1955 Volume 3 Issue 1 Pages 7-15
Published: 1955
Released on J-STAGE: April 30, 2009

DOIhttps://doi.org/10.4294/jpe1952.3.7

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Wave generations from line sources within the ground are studied. Numerical details are worked out for the line source of step function type in time. The results to be noted are as follows;
(1) At the "epicenter", the displacement is a simple pulse followed by a gradual decrease to a permanent displacement.
(2) RAYLEIGH waves appear at a certain distance from the epicenter.
(3) Permanent displacements are rather large even at points far away from the origin. They are comparable with the amplitudes of RAYLEIGH waves at the respective paints.
(4) There is no S phase in seismograms to be obtained for the wave origin of dilatational type.

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Propagation of Tremors over the Surface of an Elastic Solid.

Naota KOBAYASHI, Hitoshi TAKEUCHI

1955 Volume 3 Issue 1 Pages 17-22
Published: 1955
Released on J-STAGE: April 30, 2009

DOIhttps://doi.org/10.4294/jpe1952.3.17

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Wave phenomena, which are seen over the surface of a semi-infinite elastic solid subjected to an impulsive line force of SV and SH type, have been studied. The results obtained for the SV type origin are almost the same as for the dilatational origin. In the case of SH type origin, there is neither P wave nor RAYLEIGH wave in seismograms to be obtained.

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STONELFY Waves Generated by Explosions.

Akira KUBOTERA

1955 Volume 3 Issue 1 Pages 23-30
Published: 1955
Released on J-STAGE: April 30, 2009

DOIhttps://doi.org/10.4294/jpe1952.3.23

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Using three components seismometers, field measurements of under ground motions within bore-holes were carried out.
In this experiment, boundary waves which could be considered as STONELEY waves were obtained. The boundary surface is between layers of clay and sand and is of about 9m depth from the ground surface.
The characteristics of this wave are as follows:
Tne wave velocity is 430m/sec.
The period of motion is about 0.06 sec.
The particle trajectories are elliptical and retrograde.
The amplitude of the wave is large at the boundary surface and is decreased rapidly on leaving this surface.
These results are in good agreement with those predicted by the classical theory on the STONELEY waves.

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