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Volume 17, Issue 4
Displaying 1-8 of 8 articles from this issue
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Yutaka OHTA1964 Volume 17 Issue 4 Pages 179-186
Published: December 25, 1964
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe particle motion of the Rayleigh type dispersive waves was investigated at the earth's surface.
It was found that both M11 and M21 waves have complex features, contrary to the particle motion which might be inferred from the previous calculations. The sense of the particle motion of the M11 waves, in some cases, change twice in accordance with increase in wave length, while the M21 waves change three times as the case may be. This fact shows that the sense of the ground motion is not always a definite factor to distinguish the M waves.
Final results are summarized in Figs. 7 and 8.View full abstractDownload PDF (606K) -
Part 1. Explosions and Seismic ObservationsThe Research Group for Explosion Seismology1964 Volume 17 Issue 4 Pages 187-200
Published: December 25, 1964
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSSince November 1961, about one ton explosives were detonated three times by the Research Group for Explosion Seismology for the purpose of elucidating the crustal structure along the longitudinal line of 139°E, the boundary geologically dividing Honshu into northeastern and southwestern blocks.
Blasts were carried out at Siunzi town, Annaka city and Kawazu town, which are located in the north, middle and south part of the boundary respectively. Seismic waves from the three blasts were observed successfully by our Group at temporary stations, 52 in total, spread along the boundary up to distance of about 300km.
Observed data and travel time graphs of each observation are given in this paper. At the time of the Annaka explosion, seismic waves from a natural earthquake occurred near Miyake-jima about one minute before the scheduled shot time were observed at our temporary stations. These data as well as those obtained at J. M. A. routine stations are also given.View full abstractDownload PDF (1009K) -
Part II. Crustal StructureHiroshi HOTTA, Sadanori MURAUCHI, Tatsuo USAMI, Etsuzo SHIMA, Yoshinob ...1964 Volume 17 Issue 4 Pages 201-209
Published: December 25, 1964
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSFrom the observed data of seismic waves from Siunzi, Annaka and Kawazu explosions and a natural earthquake occurred near Miyake-jima listed in Part I of this paper, crustal structure was derived for the profile along the longitudinal line of 139°E. Although the available data obtained are not enough to draw precise picture on crustal structure, the following is proposed as a plausible one.
The superficial layer varies from 0 to 3.5km in thickness and from 1.61 to 2.83km/sec in P wave velocity. The first layer with P wave velocity of 6.00km/sec has 12km thickess under the Siunzi shot point and its lower boundary has downward inclination towards south with an angle of 1°29′. The second layer has P wave velocity of 6.82km/sec, which is observed in Japan for the first time. The boundary surface of this and the third layer, so-called Mohorovicic discontinuity, was estimated for various values of P wave velocity in the upper mantle. The depth of this surface is about 40km near Siunzi shot point and becomes deeper towards south, reaches its maximum of about 50km at around 150km away from the shot point, and then becomes shallower to about 25km near Miyake-jima.View full abstractDownload PDF (605K) -
Ikuei MURAMATU1964 Volume 17 Issue 4 Pages 210-221
Published: December 25, 1964
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSEquation of earthquake magnitude is classified as follows:
A= C (M) r-μ I
A= C (M) r-ν e-κr, κ=const. II
and log C (M)=αM+β
where A is the maximum amplitude and r is the hypocentral distance. However, Type I is not applicable to the large range of r and Type II is not for the large range of M. Accor-dingly, the following equation is proposed:
A=C (M) r-ν e-r/r c(M) III
Type III is applicable to the observed values of the large range of both r and M. As examples, the results of observation for 23 large and middle earthquakes and several explosions are shown.
It is reasonable to use the velocity amplitude for A. Then, the equation of Type I is expressed by
0.80M-0.80=logV (kine)+2 logr (km) (3)
and that of Type III is expressed by the following equations:
αM+β=log C (M)=log (Vrνer/rc)=log (Vcrcνe1) (4)
where Vc is the velocity amplitude at r=rc. For the data of 23 earthquakes of which the magnitudes are from 4.6 to 8.3, the values of M determined by Eq. (4) are well consistent with those by Eq. (3) and we get the following relations:
log C (M)=0.655M-1.719 (5)
and log rc (km) = 0.210M+ 0.947 (6)
where ν is appropriately assumed to be 1. Then we have the V-r curves for various M. These curves are well consistent with the observed values of explosions and microearthquakes, too.
The original definition of M is given by the maximum amplitude at a certain distance r0, but it is approximately available for the small range of M. Therefore, for the large range of M, r0 should be changed into .rc
If the duration of the wave group of the maximum amplitude is proportional to the hypocentral distance, the total kinetic energy of an earthquake can be related to its magnitude as follows:
log E (erg)=2 log C (M)+log c (M)+coast. (15')
=1.52M+ 11.8 (17)
for the physical constants given commonly in the earth's crust.
Equation of Type I is applicable in the vicinity of rc, so that the coefficient of log r is
-μ= (d log V/d log r)r=rc=(-ν -r/rc)r=rc=- (μ+1) (9)
Therefore, from the equations M (V, r) and M (M, r) of Type I and V=A2π/T, we have
log Tc (sec)=0.257M-1.32, at r =rc (19)
From Eq. (6) and (19), we have approximately
rc∼const.×Tc (20)
and accordingly, we see that the equation of Type III is due to the specific dissipation function Q-1.View full abstractDownload PDF (956K) -
Izuo OZAWA1964 Volume 17 Issue 4 Pages 222-232
Published: December 25, 1964
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSWe have sometimes found sudden changes of the crustal deformation in the observations with extensometers during the remarkable earthquakes. We can hard to decide that the leaps of the observed curves are not others than sudden changes of the crustal strain. But, it is rich in sincerity.
The present author has observed with extensometers the sudden changes of the crustal extensions during the earthquakes of Ryujin, Ise-Bay, Off C. Shiono-misaki, Hidakagawa, Fukui, Yoshino, Odaigahara, Kitamino and Off C. Echizen-misaki at Osakayama Observatory. These observed leaps of extensions are comparable to the magnitudes of the every earth quake. Using these leaps, he calculated the energy-changes in the crustal strains. According to his calculations, the every strain-energy changes are proportionable to the coresponding energies which are estimated from the magnitudes (M) of the every earthquake. And also, he has calculated the variations of the extensional leaps at the observatory against the azimuth in the cases of the earthquakes of Odaigahara, Kitamino and C. Echizen-misaki.View full abstractDownload PDF (794K) -
Sadao MIYAMOTO1964 Volume 17 Issue 4 Pages 233-234
Published: December 25, 1964
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (283K) -
Yasuo SATÔ1964 Volume 17 Issue 4 Pages 234-236
Published: December 25, 1964
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (334K) -
Tokuji UTSU1964 Volume 17 Issue 4 Pages 236-238
Published: December 25, 1964
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (318K)
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