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Volume 27 (1979)
- Issue 6 Pages 435-
- Issue 5 Pages 353-
- Issue 4 Pages 255-
- Issue 3 Pages 171-
- Issue 2 Pages 71-
- Issue 1 Pages 1-
Volume 27, Issue 6
Displaying 1-6 of 6 articles from this issue
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Mizuho ISHIDA, Shuzo ASANO1979 Volume 27 Issue 6 Pages 435-453
Published: 1979
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSIn order to improve the accuracy of the hypocenter locations in the Kanto district, Japan, station corrections are estimated from the data of artificial explosions. About 500 earthquakes which occurred during the period from January to August 1975 have been relocated by using the station corrections. The area covered in this study is bounded by latitudes 34.25°N and 37.25°N and longitudes 138.6°E and 141.1°E. The absolute error in the spatial coordinates of the relocated epicenter is estimated to be about 1.5km. Depth of the local explosions is estimated to be within 2km of the actual location. The good agreement between the calculated and the actual depths suggests that the accuracy of the depth is significantly improved from that determined when the station corrections were not included. An aseismic zone in the middle of the Kanto district which was suggested by the old seismicity map is not substantiated by the present study.View full abstractDownload PDF (1511K) -
Haruo SATO1979 Volume 27 Issue 6 Pages 455-466
Published: 1979
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSThe wave propagation through a one dimensional inhomogeneous elastic media is studied from a mathematical view point. An ensemble of inhomogeneous elastic media is imagined and the wave propagation is investigated statistically. The wave field inherent in these media is separated into two distinct parts: the mean wave field and the fluctuation wave field. The former can be characterized by an ensemble average of the wave fields over all the possible random media. The randomness of the media is, herein, assumed to be stationary random functions of space with zero means and small compared to the extent. The statistical property of the ensemble is characterized by the cross correlation functions of the random inhomogeneities. The manner in which the mean wave field profile is modified by the scattering from the random inhomogeneities is discussed in detail. The equation governing the mean wave field up to the second order of the inhomogeneities is derived. The dispersion relation shows the gradual decay and the dispersive manner of the mean wave field in the media in which the inhomogeneities spread over a large region of space. The attenuation which characterize the exponential decay of the mean wave field is calculated for two examples and discussed.View full abstractDownload PDF (918K) -
Roger N. ANDERSON, Richard K. NISHIMORI1979 Volume 27 Issue 6 Pages 467-480
Published: 1979
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSGabbro, gabbroic anorthosite, basaltic breccia, diabase and basalt samples were dredged from a fracture zone of the Galapagos Rise, a fossil spreading center on the Nazca plate. Serpentinite was dredged from the Ecuador fracture zone of the Galapagos Spreading Center. Although the rocks are variably altered, minerals and chemistry of gabbroic rocks indicate that extensive fractionation occurred throughout the suite. Basaltic breccias have textures indicating prefracture zone brecciation.View full abstractDownload PDF (4504K) -
Hideo HANADA1979 Volume 27 Issue 6 Pages 481-496
Published: 1979
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSEffects of earth and oceanic tides on the Earth's gravitational constant, hereinafter called gravity for short, are estimated for precise gravity measurements in Izu peninsula. In calculating the oceanic effects, we apply Green's function given by Farrell to hourly tidal records obtained at the nearby tidal stations and to the tidal charts given by Tiron et al. As a result, the oceanic effect ranges from about 5 to 10μgal in the peninsula. This fact may lead to the conclusion that hereafter, the oceanic tidal correction seems to be necessary for precise gravity measurements. The optimal tidal factor of gravity (G-factor) and phase lag used in the earth tidal corrections are estimated as 1.15 with a phase lag of 0.1 hour, although we have usually adopted a G-factor of 1.20 without any phase lag. The difference between gravity values corrected with the usual tidal constants and ones estimated in the present study amounts to about 5μgal.View full abstractDownload PDF (1354K) -
Shuzo ASANO, Nozomu DEN, Hiroshi HOTTA, Toshikatsu YOSHII, Yoichiro IC ...1979 Volume 27 Issue 6 Pages 497-509
Published: 1979
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSRefraction measurements by the two ship method were conducted in July 1969 in the deep sea terrace of Hidaka, Hokkaido. The general features of the crustal structures derived are similar to those in the adjacent oceanic areas. Thick sediments cover the whole area, especially its northernmost part. The layer with a P-wave velocity of 6km/s is found in all profiles. That is, the crustal structure in this area is continental and similar to that off the Sanriku area.View full abstractDownload PDF (933K) -
Yoshiyuki KANEDA, Noritake NISHIDE, Yoshimi SASAKI, Shuzo ASANO, Toshi ...1979 Volume 27 Issue 6 Pages 511-526
Published: 1979
Released on J-STAGE: April 30, 2009
JOURNAL FREE ACCESSIn 1977 and 1978, three explosions of 500kg were carried out in a reclaimed land, Yumenoshima, in the northern part of Tokyo Bay, and a quarry blast was made at Inabu in the northeastern part of Aichi Prefecture, Central Japan. Seismic waves generated by these four explosions were observed for an investigation of crustal structure in the western Kanto district. A distinct late arrival was recorded in seismograms from Yumenoshima explosions. Mainly from the travel time analysis, this arrival is identified with the reflected wave from the Mohorovicic discontinuity. Combining travel times of the reflected wave with those of first arrivals, a model of crustal structure in the western Kanto district is derived. It is found that the crust thickens toward the Fossa Magna and its thickness is about 38 to 45km.View full abstractDownload PDF (1025K)
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