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Volume 26, Issue 4
Displaying 1-10 of 10 articles from this issue
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Junzo KASAHARA, Sadayuki KORESAWA, Kenshiro TSUMURA, Shozaburo NAGUMO, ...1973 Volume 26 Issue 4 Pages 305-315
Published: December 30, 1973
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe earthquake of M=7.0 occurred in the east off Hachijo-jima, February 29, 1972. We observed the aftershocks at Hachijo-jima, Boso peninsula and Dodaira Seismographic Network, and determined the hypocenters of the aftershocks. The preseismicity near aftershock area was also studied. The aftershocks occurred at the area from 141° E to 141°20′ E and from 33°15′ N to 33°40′ N. The aftershock locate on the plane steeply inclining from north to south. The western end of aftershock area is very sharp. The main shock occurred at the south-east edge of aftershock area. The aftershock area was examined by using different velocity models. Although the absolute position of aftershock epicenter using Kanto velocity model is not same as one using J-B model, other results using two models are similar. The aftershocks area is south east of that of the earthquake off Boso peninsula, 1953. The earthquakes from Aug., 1971 to Dec., 1972 occurred at the area from ENE to WSW. We observed the T-phase at Hata station from earthquakes under Izu-Mariana trench.View full abstractDownload PDF (853K) -
Tatsuhiko WADA, Kosuke KAMO, Tamotsu FURUZAWA, Kensuke ONOUE1973 Volume 26 Issue 4 Pages 316-325
Published: December 30, 1973
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSAt the landslide area many cracks are found generally. In order to examine the effect of the existence of cracks on microtremors, the observation of microtremors over the Kamenose landslide area were carried out in March and July, 1971 and April, 1972. From the wave form of the filtered records and the Fourier spectrum of microtremors, the following results were obtained.
1. In medium frequency range (2-5Hz), the amplitude of the filtered records, the peak of the amplitude spectrum and the direction of the polarization of the particle motions are affected strongly by the existence of cracks.
2. Low frequency range (lower than 1Hz) may have reflected the global structure all over the Kamenose area.View full abstractDownload PDF (775K) -
Junzo KASAHARA, Sadayuki KORESAWA, Isao NAKAMURA, Kenshiro TSUMURA, Sh ...1973 Volume 26 Issue 4 Pages 326-335
Published: December 30, 1973
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSOn December 4, 1972, an earthquake of M=7.2 occurred near the aftershock area of an earlier earthquake east of Hachijo-jima, February 29, 1972. We carried out aftershock observations at Hachijo-jima. We determined hypocenters of foreshocks. Clearly, three foreshocks occurred from 3 days to 5 hours before the main shock. The locations for three foreshocks are inside and eastside of the aftershock area for the earthquake, December 4. The main shock occurred at the eastward boundary of aftershock area for this, and then aftershock expanded to westward. The aftershock area is connected to the westside boundary of that for the earthquake, February 29. The size of aftershock area in December, 1972, is about 60km×40km, and larger than that of aftershock in March, 1972. The aftershocks occurred on the plane steeply inclining from north to south. In order to interpret the occurrence of these two earthquakes east of Hachijo-jima, we proposed a model.View full abstractDownload PDF (772K) -
Yasuhiro UMEDA1973 Volume 26 Issue 4 Pages 336-347
Published: December 30, 1973
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSA wide band seismograph system of portable type was devised to make the temporary observation of long-period seismic waves easily. This system consists of an electromagnetic seismometer with pendulum of 1.0Hz, electrical R-C integrating circuit, IC operational amplifiers, and a long term data recorder. In order to get a broad frequency response curve and a large dynamic range for seismic waves from 0.1 to 100Hz, the output of this system was recorded on the magnetic tape, being deviled into the three channels named LONG, MIDDLE and SHORT, respectively.
An earthquake of magnitude 6.0 occurred in the east of Fukui Prefecture on August 31, 1972. Three temporary array stations with the wide band seismograph systems were set up at a short distance from the focal area. Eight aftershocks (2.15≤M≤4.5) recorded with this systems were analyzed by using an analogue type band-pass filter.
The spectrum thus evaluated was found not to have any fiat portion at longer period, but to have plausible peak regardless of the spectra for P, S wave groups and maximum amplitudes. The frequency corresponding to the peak of spectrum varies merely with the magunitude of earthquake, but not with the layered structure beneath the station nor with the focal distance. The peak frequency, therefore, may be related to some of the source parameters. Another interesting fact is that the shape of the spectrum becomes broader with the earthquake magnitude, that is, the half-value width, for example, is widening with inceasing magnitude.View full abstractDownload PDF (1069K) -
Mahito UCHIDA1973 Volume 26 Issue 4 Pages 348-354
Published: December 30, 1973
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSBy using the data of recently developed Microearthquake Observatory net, we can determine the hypocenters of deep focus earthquakes exactly. Focal planer zones are found to be more thiner than the ones determined hitherto, for example, those of the earthquakes (T) near Takayama, Gifu Prefecture and (W) near The Wakasa Bay is ten and a few km thick. The distribution of hypocenters in the north area of Kinki district are different from those in the south: the former is discontinuous, but the latter is continuous distribution.View full abstractDownload PDF (500K) -
Shuichiro HORI, Ziro SUZUKI1973 Volume 26 Issue 4 Pages 355-361
Published: December 30, 1973
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe epicenter of the Numadate Earthquake on March 28, 1914 (JMT) has been reported to be at 140°.9E, 39°.8N in the “Rika-Nenpyo”, which is a standard reference on big earthquakes in Japan. However, this location is inconsistent with the distribution of damage or with other evidences. The epicenter is relocated in this paper based on the newly collected reports about damage as well as the S-P times at several stations. Both the macroseismic and instrumental results give the epicenter at 140°.4E, 39°.2E.View full abstractDownload PDF (686K) -
-In Relation to the Fault-like Lines Discovered by ERTS-I- (preliminaries)Katsuhiko ISHITBASHI1973 Volume 26 Issue 4 Pages 362-367
Published: December 30, 1973
Released on J-STAGE: March 11, 2010
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Shoji SAKATA1973 Volume 26 Issue 4 Pages 367-368
Published: December 30, 1973
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (232K) -
Shoji SAKATA1973 Volume 26 Issue 4 Pages 369-370
Published: December 30, 1973
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (238K) -
Kanto DistrictMasaru TSUJIURA1973 Volume 26 Issue 4 Pages 370-375
Published: December 30, 1973
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (565K)
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