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Volume 7, Issue 4
Displaying 1-6 of 6 articles from this issue
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Yoshibumi TOMODA1955 Volume 7 Issue 4 Pages 201-208
Published: March 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSInstead of usual harmonic analysis [(ambm)=1/π∫2πf(t)cossinmt dt], [(a′mb′m)=1/π∫2πf(t)φ(mt)φ(mt)dt] is adopted as a first approximation, where φ (mt) are square wave functions having wave number m within 2π. The relations between (ambm) and (a′mb′m) were derived. Using these relations, we can obtain (ambm) from (a′mb′m) more easily than by the usual mothods.View full abstractDownload PDF (341K) -
The Research group for Explosion Seismology1955 Volume 7 Issue 4 Pages 209-215
Published: March 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSSeptember 13th, 1953, nearly 42 tons of explosives were detonated at Kamaisi Mine, Iwate Prefecture in the northeastern part of Japan. Location of the explosion was almost the same as the first explosion in the Kamaisi Mine of 1952. Observations of seismic waves generated by the explosion were made at fifteen temporary stations set up in the north-south directions.
Special care was teken for time keeping, and some improvements were made in the instruments.
The results of the observations are interpreted as follows:
(1) No surface layer is found. (very thin if any)
(2) From an analysis of P wave velocity, a layer of 6.05km/sec with a thickness of 22.2km or 25.6km overlies the second layer of 7.27km/sec or 7.55km/sec.
(3) From an analysis of S wave velocity, a layer of 3.46km/sec with a thickness of 32.4km. or 35.8km overlies the second layer of 4.57km/sec or 4.75km/sec.
(4) From an analysis of reflected waves, the thickness of the layer of 6.05km/sec. is 22.13km.
The uncertainty of the velocity in the first layer and an existence of Pn layer of 8.2km/sec will be studied more closely in the next opportunity.
Remark: The interpretation is based on the present observations alone, and other series of observations in the same region are entirely neglected. Therefore the present paper shows only apparent features. A general analysis on all available data has been oraly presented and will be published in the near future.View full abstractDownload PDF (613K) -
Isao TORIUMI1955 Volume 7 Issue 4 Pages 216-225
Published: March 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThis paper treats of the vibrations in cylindrical foundation of machine on the surface of a semi-infinite homogeneous elastic solid. Infinite integrals are solved graphically on the complex plane. The results are illustrated in figures and a numerical example is shown.View full abstractDownload PDF (548K) -
Ituo TAMAKI1955 Volume 7 Issue 4 Pages 226-232
Published: March 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThis is continued from the previous paper of the same title. Summary of the present paper is as follows. (1) Corrections and additions to the Crustal structure . which mentioned in the previous paper are shown in Figure 1. (2) Horizotal structures at the surface and at the depth of 10km., 20km., 30km., and 40km. are derived from the vertical structures, and illustrated in Figure 3-7. (3) The distributions of observed gravity anomalies are well consistent with the lateral structure of the crust now determined by the author's. (4) The analogies between geological structures and the author's one are discussed. The median line and Fossa Magna are able to point out in the vertical structures. (5) The observed deviations of incident times of P waves of deep earthquakes agree well with the same deviations calculated from the author's structures. The last problem will be mentioned again in the following paper.View full abstractDownload PDF (621K) -
Tokuji UTSU, Akira SEKI1955 Volume 7 Issue 4 Pages 233-240
Published: March 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe after-shock regions of 39 shallow earthquakes which took place in and near Japan (Table 1) are determined and the relation between thier areas and the magnitudes or energies of main-shocks is investigated. If we assume that the logarithm of the area A (km2) and the magnitude M are in linear relation, i. e., logA=aM+b (Fig. 2-3), the constants a and b become as follows,
a=1.02±0.08, b=-4.01±0.57 (for 39 total earthquakes)
a=0.93±0.08, b=-3.18±0.61 (for 23 oceanic earthuakes)
a=0.85±0.10, b=-3.05±0.72. (for 16 land earthquakes)
From the relation between M and E (erg), we get A∝Em, where m≈1/2, then E/A∝A∝√E, this means that the surface density of energy increases as the energy increases.View full abstractDownload PDF (583K) -
K. AKAMATU1955 Volume 7 Issue 4 Pages 241-247
Published: March 30, 1955
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe result of applying the differential transformer of variable inductance type to the seismograph as a transducer proportional to displacement has been satisfactory.
The merits of the differential transformer are as follows:
1. It satisfies our requirement for linearity over a wide range of displacement.
2. As a seismograph it is compact in size and simple in design. The circuit for vacuum tubes is also simplified.
3. It is readily possible to increase the magnification to 105 by amplifier circuits.
Microtremors and microseisms have been recorded by attaching electrodynamic transducer (moving coil type) and differential transformer to the pendulum of a seismogrpah with a period of 1 second. In using the velocity seismograph (electrodynamic transducer attachment) with an integrating circuit hooked up to the amplifier circuit, at Hongo in Tokyo, when the time constant is raised to 4 sec., the results agree with those of displacement seismograph (differential transformer attachment).View full abstractDownload PDF (569K)
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