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Volume 31, Issue 1
Displaying 1-13 of 13 articles from this issue
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Shear Wave in Wood's AlloyHiroaki KAMIOKA1978 Volume 31 Issue 1 Pages 1-9
Published: March 31, 1978
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSShear wave velocity and its attenuation in Wood's alloy were measured from room temperature to melting range. The present data are combined with those for dilatational wave, and the variations of elastic and anelastic properties during the melting process were analyzed. Although the shear wave vanished at the early stage of melting process, the rigidity was supposed to decrease continuously to zero at the end of total melting. The variations of the other quantities associated with melting were discussed based on the present data.View full abstractDownload PDF (716K) -
Tsutomu SASATANI, Minoru KASAHARA1978 Volume 31 Issue 1 Pages 11-23
Published: March 31, 1978
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSStrain seismograms from near earthquakes observed at the Erimo Geophysical Observatory are analyzed. Wave forms of these strain seismograms from P arrival to S arrival are relatively simple. Theoretical strain seismograms from the double-couple point source are calculated and are compared with the observed strain seismograms. A good agreement between the observed and the theoretical strain seismograms from P arrival to S arrival is obtained. Seismic moment and effective rise time of the moment rate function are estimated. It is demonstrated that the strain meter is very useful to record the slow deformation such as the Kurile islands tsunami earthquake of June 10, 1975.View full abstractDownload PDF (1175K) -
Tokutaro HATORI1978 Volume 31 Issue 1 Pages 25-33
Published: March 31, 1978
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSRelation between tsunami magnitude m, (Imamura-Iida scale) and seismic moment M0, is investigated, using the data of 30 tsunamigenic earthquakes on the Pacific coast. The source area of tsunami is very well represented by the formula: log S=0.4m+3.3, where S is measured in square kilometers. The tsunami magnitudes m=1, 2, 3 and 4 correspond to the seismic moments of the order of M0=1027, 1028, 1029 and 1030 (dyne-cm), respectively. The tsunami magnitude due to the dip angle thrust faulting δ≥30° has a tendency to increase. It is useful information that the tsunami data be used a diagnostic aid in estimating seismic moment.View full abstractDownload PDF (724K) -
Kunihiko WATANABE, Norio HIRANO, Yoshimichi KISHIMOTO1978 Volume 31 Issue 1 Pages 35-47
Published: March 31, 1978
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSA telemetering observation of microearthquakes started in May 1976, at the Hokuriku Microearthquake Observatory, Disaster Prevention Research Institute, Kyoto University. In this article, seismicity in the Hokuriku area was investigated, using the data by the telemetering observation for 14 months since May 1967, and historical data of large earthquakes.
The microseismicity is high in the areas from Fukui plain to the north-eastern side of Lake Biwa and from west coast of Lake Biwa to Wakasa Bay. On the contrary, microseismicity is relatively low in the areas of Lake Biwa, off-shore of Japan Sea, and the northern part of Gifu and Ishikawa prefectures.
The microseismicity in this area seems to be closely related to large tectonic structures, such as Fukui earthquake fault, Neodani fault, and Yanagase fault. These active faults, in general, form boundaries between seismically active and aseismic areas.
The active areas of microearthquakes at present are almost coincident with those of disastrous earthquakes in the past. In regard to the activities of the past disastrous earthquakes, there seems to be some regularities of occurrence spacially and temporally.View full abstractDownload PDF (1209K) -
Yoshiteru KONO1978 Volume 31 Issue 1 Pages 49-62
Published: March 31, 1978
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSA computer program is reported which displays the time- and space-variation of seismicity in a chosen area. A refresh type computer graphic display unit is employed as a display unit for this purpose. This program has the following functions; (1) to draw a map of a particular area based on a prescribed map projection method; (2) to display the earthquakes. successively on the map in chronological order of occurrence; (3) to plot a symbol at the earthquake epicentre, which characterises the magnitude and focal depth of the event; (4) to erase the earthquake symbol from the display, after some specified time interval; (5) to display a time and date. During a run of the program, the following operations can be applied; (1) the display can be temporarily “frozen”; (2) the following parameters can be altered: (i) the ratio of real and simulation time; (ii) the duration of the display of each earthquake, (iii) the time and date.
Some results of display experiments are illustrated in this paper: (1) World Seismicity, particularly before and after the Kanto earthquake (2 Sept. 1923; M=7.9); (2) The seismicity of the Japanese islands, particularly before and after the Niigata earthquake (16 Jun. 1964; M=7.4), and (3) local seismicity in northeastern Japanese islands, particularly before and after the 1968-Tokachi-Oki earthquake (16 May 1968; M=7.9).
These experiments suggest that studies of the temporal variation of the pattern of seismicity are important because they allow: (1) recognition of some characteristic features. of earthquake occurrence, as a basis of all seismological studies; (2) an understanding of the nature of the present seismicity in the light of the past seismicity; (3) comparison of the results of laboratory experiments on the failure of materials with the real seismicity; (4) correlation of the seismicity with other natural phenomena such as volcanism, crustal deformation etc.; (5) the detection of hidden regularities in the seismicity pattern.View full abstractDownload PDF (1534K) -
Kennosuke OKANO, Shozo KIMURA, Tadashi KONOMI1978 Volume 31 Issue 1 Pages 63-72
Published: March 31, 1978
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe seismic activity in the central and eastern part of Shikoku District is investigated by using data from Kochi and Tokushima Observatory networks. The focal depth distribution shows two distinct groups of earthquakes. The first group of earthquakes with shallower focal depths (H<20km) has the pressure axis in E-W direction and the second one with deeper earthquakes (H>20km) has the pressure axis in N-S to N10°W-S10°E direction. Earthquakes determined foci are distributed nearly in the southern part of the Median Tectonic Line and the aseismic activity in the northern part of M. T. L. is noticeable. It seems that aseismic epicentral zones of shallower earthquakes are complemented by seismic activities of deeper ones. It is suggested that the shallower earthquakes are generated by the stress originating from the tectonic activity represented by the deeper ones. The b values of the shallower and the deeper activity regions are estimated at 0.98 and 0.74, respectively. The difference of these b values may be indicative of the respective characteristics of the regions generating earthquakes. However, we cannot definitely conclude it, because the difference of hypocentral distances of these earthquake groups is closely related to the magnitude estimation. The annual variation of seismic activities is examined from the b values for these two regions. But no remarkable trend is noticed.View full abstractDownload PDF (922K) -
Yuzo ISHIKAWA, Takashi MIYATAKE1978 Volume 31 Issue 1 Pages 73-86
Published: March 31, 1978
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSAn attempt was made to detect some anomalies precursory to earthquakes, by applying the Wiener's predictive filter to the records of crustal strains, tilts and seismicity. The present technique finds the anomalies if there are large residuals between the observed data at a certain time and their predicted values computed from the past data over a finite period.
Pre-seismic tilt changes have been confirmed by this method in the case of the 1943 Tottori earthquake from the record obtained at the Ikuno station, but in other cases precursory phenomena are not definitive. It appears that there were post-seismic strain changes after the 1969 central Gifu earthquake on the record obtained at the Kamitakara station, and also after the 1952 Yoshino earthquake on the record at the Ide station.View full abstractDownload PDF (1330K) -
Tsutomu TERASHIM, Kunio OZAWA1978 Volume 31 Issue 1 Pages 87-93
Published: March 31, 1978
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSRecently, it is suggested that the behavior of underground water plays an important role as a trigger to generate the earthquakes.
Studies are made in the present paper on the variations of flow rate, temperature and heat capacity of hot springs in Izu peninsular since 1968 to 1976.
The patterns of these variations show good correlations with the recent crustal movement and gravity variation in the same area.
Above fact leads to the possibility to use the variations of the data on hot springs as one of the precursor of the generation of a large earthquake.View full abstractDownload PDF (632K) -
Hajimu KINOSHITA, Masashi YASUI1978 Volume 31 Issue 1 Pages 95-100
Published: March 31, 1978
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSA Simple, low cost and easy to handle digital recording and retrieval systems are described. The apparatus is to be used in recording a slowly changing analog signal. One set of data consists of 16 pairs of pulses. Time interval between two pulses in a pair is 10msec. and that between successive two pairs is 100msec. Pulse width is variable between 1 to 5msec. Combinations of pulses in a pair are (1, 0) which denotes that the data of this bit is zero, or (1, 1) denoting one (i. e. high level). The first pulse in a pair is always high and is used as a clock pulse in a data retrieval. One of the merits of this system is that we can use an ordinary tape recording device without special precautions such as wowfluttering of a driving mechanism or snaking of a magnetic tape.View full abstractDownload PDF (2480K) -
Takuo HIRONO1978 Volume 31 Issue 1 Pages 101-111
Published: March 31, 1978
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSA countercurrent accompanying the descending lithosphere is inferred to exist under Northeastern Honshu from our earthquake activity charts previously published. The countercurrent is a band of thermal convection lying between the coast of the Sea of Japan and the Aseismic Front defined as the western boundary of the seismic region in the district, at the level of 60km depth. Heat source for the convection lies on the top edge of the slab just under the Volcanic Front, which is the centerline between the horizontal limits of the convection. The motive power of the convection is magma produced by frictional heating between the upper mantle and the descending slab.
The dimensions of the convection are, in vertical section, 120km in depth, 160km in width. It approximately satisfys the theoretical demand for the existence of thermal convection, that is, the dimension ratio of 1.2, and Rayleigh number of the order of not less then 103. Deviatric stress along the bottom of the convection adjacent to the top edge of the slab is shown theoretically as vertically compressional that is in accordance with Umino-Hasegawa observation.
The upper part of the convection descending eastward forms a slanting layer which hits the flank of the descending slab at the middle depth of the convection, 60km, and then turns toward the heat sourse. Momentum change brought about by the abrupt directon chang of the current results in a bending moment exerted on the descending slab, which, forming a couple with another one exerted on it at the trench axis, causes a pure bending of the slab between the trench and the middle point of the convecton.View full abstractDownload PDF (1181K) -
Kiyoshi ISHII1978 Volume 31 Issue 1 Pages 113-115
Published: March 31, 1978
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (294K) -
Tatsuto IINUMA, Hideteru MATUMOTO, Michio TAKAHASHI, Toshimitsu TSUKAK ...1978 Volume 31 Issue 1 Pages 115-116
Published: March 31, 1978
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (215K) -
Yasuo SATÔ1978 Volume 31 Issue 1 Pages 117-118
Published: March 31, 1978
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (192K)
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