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Volume 10, Issue 2
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Kenshirô TSUMURA1957 Volume 10 Issue 2 Pages 67-78
Published: October 25, 1957
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe Japanese coast, on both the Pacific and Japan Sea sides, can be divided into several regions, in each of which the monthly mean sea-levels at mareograph stations change almost identically. One of the most remarkable boundaries between such regions is located near the southern end of Kii-Peninsula, Honshû.
If two stations are situated in the same one of such regions as above mentioned, the change in the difference of monthly mean sea-levels between those stations may more conveniently be used for studying the vertical crustal deformation at the place than that in the monthly mean sea-levels themselves, because the former is less irregularly disturbed by meteorological and oceanographical effects.
The change in the difference of daily mean sea-levels between selected stations can also be used for tracing the detailed process of vertical crustal deformations.
By these procedures, the vertical crustal deformations before and after destructive earthquakes have been investigated. The results obtained are shown in figures.View full abstractDownload PDF (1186K) -
Tomeo NAGAMUNE, Akira SEKI1957 Volume 10 Issue 2 Pages 79-85
Published: October 25, 1957
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESS1) The formulas have been deduced by the method of least squares by which to determine the magnitude M of a distant shallow-focus earthquake from surface wave data obtained at Matsushiro Seismological Observatory. These are
M=logA+1.32logΔ+4.11(for 30sec period) (2) and M=logA+1.31logΔ+4.28(for 20sec period), (3)
where A is the surface wave ground amplitude expressed in micron, Δ the epicentral distance in 1, 000km and log is the common logarithm.
If, instead of the amplitude A, we use (A/T) which is proportional to the ground velocity, we get from the equations (2) and (3),
M=log(A/30)+1.32logΔ+5.58 (4) and M=log(A/20)+1.31log Δ+5.58 (5)
which are almost exactly the same. We may write
M=log(A/T)+1.31logΔ+5.58. (6)
2) The energy E′ of RAYLEIGH waves has been calculated for each of 16 selected shallow earthquakes, using seismograms obtained with the Galitzin and the Long Period seismographs working at Matsushiro. The magnitudes of the earthquakes range from 5.4 to 8.1. The energy E′ and the magnitude M have been found to be connected as follows
logE′=(1.98±0.074)M+(6.65±0.48). (9)
If the total energy E of an earthquake is assumed to be twice the energy of RAYLEIGH waves, then follows the relation:
logE=1.98M+6.95. (10)View full abstractDownload PDF (508K) -
The Research Group for Explosion Seismology1957 Volume 10 Issue 2 Pages 86-96
Published: October 25, 1957
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSAt 01h 35m, 03h 35m on May 1, and again at 01h 35m, 03h 35m on May 3, 1954, four explosions were fired near Kamaisi Mine following the two former explosions of Dec. 7, 1952 and Sept. 13, 1953 in the same locality. The amount of charge of 01h 35m and 03h 35m explosion was 0.1 and 1.0ton respectively. 17 temporary observation stations were spread towards west and south for about 30km from Kamaisi City. Each station was equipped with high-sensitive electro-magnetic seismometers with amplifiers. These explosions were planned in order to ascertain the results obtained by the former five explosions about the crustal structure of the north-eastern part of Honsyû, i. e., the interface between the layers specified by the velocities 5.8km/sec and 6.1km/sec of P wave is shallower towards east and come across the earth surface near Kamaisi City. By the present explosion experiments these results were confirmed. It has become certain that there is an anticline of the layer with velocity 5.8km/sec of P wave, the axis of which is under the line connecting the shot points B and C and parallel to it. The final conclusion is graphically shown in Fig. 9.View full abstractDownload PDF (992K) -
Harumi AOKI1957 Volume 10 Issue 2 Pages 97-106
Published: October 25, 1957
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSWave noises or coda part of seismic waves may be interpreted as composed of single or multiple reflection waves as well as of dispersive or induced surface waves. Sometimes reflection waves observed on seismograms are due to various composite reflections caused by a set of closely spaced reflecting surfaces. Here we assume that the wave medium consists alternatively of two kinds of elastic layers whose thickness is such that the wave travelling time through each layer is just the same. Since this is a kind of regular system, it may represent the case of largest effect of multiple reflections.
The results obtained theoretically in this paper are as follows;
1) Reflections of higher orders cannot be neglected.
2) In our rough estimation, the general appearance of resulting waves is determined by the value “Na”, where N is the number of layers between the source and the receiving point, “a” is a constant relating to the reflecting factor “k” (a=k2/1-k2).
3) The attenuation and reverberation of waves and elongation of wave length are noticed in some cases, but their characters are too much complicated to be expressed in a simple formula.
4) The wave reverberation is remarkably reduced for long waves and a very long wave (the wave length more than eight times of the thickness of a layer) travels as if it were propagated through a homogeneous medium, though there can be seen some slight change in its wave form.View full abstractDownload PDF (762K) -
Kyôzi TAZIME1957 Volume 10 Issue 2 Pages 107-109
Published: October 25, 1957
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (347K)
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