Zisin (Journal of the Seismological Society of Japan. 2nd ser.)

A Consideration about the Mechanism of Occurrence of Large Earthquakes. (II)

Saburo KOMURA

1957 Volume 10 Issue 1 Pages 1-5
Published: August 25, 1957
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.10.1_1

JOURNAL FREE ACCESS

Show abstractHide abstract

In the previous paper, it was pointed out that the period of the first maximum ground motion due to an earthquake as observed at various seismological stations shows a systematic pattern of distribution with respect to the azimuthal angles of the stations as seen from the origin of the earthquake. This regularity was accounted for by assuming that the seismic crack which is composed of a series of small cracks and from which seismic waves are generated is developed with a certain definite velocity from one of its ends to the other along either one of the nodal lines of initial motions and the period of waves originating from the crack and being propagated into various directions are modified according to Doppler effect.
In the present paper, the writer has applied the idea above mentioned to observational data for Kita-Tango (Mar. 7, 1927), Kita-Izu (Nov. 26, 1930), Shizuoka (July 11, 1935) and Tokachi-Oki (Mar. 4, 1952) earthquakes with satisfactory results.

View full abstract

Download PDF (1900K)
On the Magnitudes of Earthquakes

Chuji TSUBOI

1957 Volume 10 Issue 1 Pages 6-23
Published: August 25, 1957
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.10.1_6

JOURNAL FREE ACCESS

Show abstractHide abstract

This is the synopsis of one of the opening lectures at the symposium “Magnitudes of Earthquakes” which was held on April 15, 1957, at the Annual Meeting of the Seismological Society of Japan. First, history of the magnitude scale was briefly sketched and special attention was called to the assumption originally made by C. F. RICHTER that the ratio of maximum amplitude due to an earthquake to that due to the standard (M=0) earthquake depends only on the magnitude of the former and does not depend on the epicentral distance. Then followed the discussions of the relation between the maximum amplitude A and epicentral distance Δ, in particular reference to Japanese earthquakes. Various formulas by which to derive M from Δ and A were compared. The number N of earthquakes in terms of their magnitudes was the next subject of talk. It was pointed out that earthquakes in and near Japan are contributing well over 10% to the total number of earthquakes in the whole world. Then the amount of energy released by earthquakes was surveyed. Japan's contribution was estimated to be 0.5×10²⁴erg/year in total or 1.5×10³erg/cm² year. This value 0.5×10²⁴erg/year is again more than 10% of the total energy for the whole world which was estimated by the present writer to be 3.6×10²⁴erg/year (one third of GUTENBERG's value.) Finally, the relations among M, E, V (earthquake volume), A (aftershock area), and x (ultimate strain of the crustal material) were discussed from the writer's own view point. The lecture closed with suggestions for future problems.

View full abstract

Download PDF (1706K)
Frequency Distribution of Earthquake Magnitude, Seismicity and Related Problems

Toshi Asada

1957 Volume 10 Issue 1 Pages 24-34
Published: August 25, 1957
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.10.1_24

JOURNAL FREE ACCESS

Download PDF (1477K)
Magnitude of Earthquakes and Occurrence of their Aftershocks

Tokuji UTSU

1957 Volume 10 Issue 1 Pages 35-45
Published: August 25, 1957
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.10.1_35

JOURNAL FREE ACCESS

Download PDF (1056K)
[title in Japanese]

1957 Volume 10 Issue 1 Pages 46-54
Published: August 25, 1957
Released on J-STAGE: March 11, 2010

DOIhttps://doi.org/10.4294/zisin1948.10.1_46

JOURNAL FREE ACCESS

Download PDF (796K)

Register with J-STAGE for free!