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Volume 35, Issue 1
Displaying 1-14 of 14 articles from this issue
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Kiyoyuki KISIMOTO1982 Volume 35 Issue 1 Pages 1-18
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSIn the field of earthquake engineering, the knowledge of anelastic properties of soil layers as well as elastic properties to the depth of about a hundred meters is necessary for predicting the dynamic response of soils and man-made structures. Reliable in-situ measurements of wave attenuation in soil layers, however, are small in number. For the purpose of measuring anelastic properties in soil layers, experiments were carried out at two places in the southern part of the Kyoto basin. In the data obtained by means of a small surfacetraction source, Love-wave phase is dominant in amplitude. Using the extended Haskell's layer-matrix formula, QS values of soil layers to the depth of about ten meters were estimated by synthesizing the observed Q values for Love-wave. Formulas used in the calculation are more general in the sense that they contain no low-loss (i. e. Q>>1) assumption for the medium. These formulas can be used for both body waves and surface waves of multilayered anelastic media. Obtained QS values of soil deposit are 10 to 20 at one site, and 10 to 30 at the other site.View full abstractDownload PDF (1510K) -
Shukyo SEGAWA, Hiroyuki HAMAGUCHI, Kazuhiko GOTO1982 Volume 35 Issue 1 Pages 19-33
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThe detailed investigations of the deep seismic zone beneath the island arc have revealed the existence of the double-planed structure of the intermediate-depth seismic zone. The characteristic features of the double-planed structure have been interpreted in terms of phase change, unbending, thermal stress or sagging of the descending plate beneath the island arc. The purpose of the present study is to simulate the double-planed structure experimentally based on our thermal stress model and to clarify the relationship between the thermal stress distribution and the foci of acoustic emissions (A. E.) in a sample.
The sample used in this experiment is pine resin with the diameter of 10cm and the thickness of 2.5cm. The sample is, first, gradually cooled to the uniform temperature of -30°C. Then, one of the sample surfaces is uniformly heated up to 20°C with the three heating rates of 2.0, 5.5 and 14.5°C/min and a non-uniform temperature distribution along the direction of the sample thickness is generated. Acoustic emissions during the heating process are detected and located using the four piezo-electric transducers which are set up on the both surfaces. The thermal stresses in the sample are estimated based on the observed temperature distribution. The regions near the upper and lower surfaces are characterized by the compressional stress with the maximum value of 25 to 70 bars depending on the heating rate, whereas the region near the middle part is characterized by the tensional stress with the maximum value of 15 to 50 bars. The focal depth distributions of A. E. are separated into three groups by the two planes with the null thermal stress. The two groups are located in the regions of the compressional thermal stress and the other is in the region of the tensional stress. The triple-planed A. E. activity induced by the thermal stresses does not correspond exactly with the double-planed seismic activity in the descending plate. This discrepancy, however, is mainly attributed to the high temperature state near the lower rim of the descending plate. The present model experiment confirms that the occurrence of the double-planed seismic activity beneath some island arcs can be explained in term of the thermal stresses induced in the descending plate.View full abstractDownload PDF (1475K) -
Yoshinobu TSUJI1982 Volume 35 Issue 1 Pages 35-51
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSIn the evening of November 7, 1855, a large earthquake occurred beneath the sea off the southern coast of the Tokai district, central part of the Honshu Island. Recently more than fifty kind of historical documents were discovered, and we obtained much amount of knowledge about it. Most serious damages occurred in several villages on the coast in the vicinity of Hamamatsu City, where destruction of houses and gushing of sand were reported. Shock of intensity IV (in JMA scale) was experienced in the western part of Shizuoka Prefecture and at several cities on the east coast of the Kii Peninsula. After the occurrence of the earthquake, a small tsunami was generated, and was observed at the Shimoda Port near the tip of the Izu Peninsula, and at three ports on the east coast of the Kii Peninsula, where inundation height was one to two meters. The coast was upheaved near the mouth of the lake of Hamana where it had been subsided with the occurrence of the Ansei Tokai Earthquake of December 23, 1854. In contrast to that, the coast near the cape of Omaezaki was subsided with this earthquake, which had been upheaved with the Ansei Tokai Earthquake.
The estimations of the location of the epicenter and the magnitude were made by adapting least mean square method to the formulae which give the relationship between the magnitude and the area of intensities IV, V, and VI. The location of the epicenter and the magnitude are estimated 34.5°N, 137.8°E and M=7.1, respectively.View full abstractDownload PDF (1721K) -
Masami OKADA1982 Volume 35 Issue 1 Pages 53-64
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSMonthly distribution of major shallow earthquakes (M≥7.5) in and near Japan is investigated using earthquake catalogs including pre-instrumental data. Major shallow earthquakes off Hokkaido and Sanriku districts are concentrated in spring, and those along the coast from Miyagi prefecture through Shikoku district occurred more frequently from August to December, as Mogi has pointed out. We suggest with some consideration that these variations are statistically significant at a 95% confidence level. In the other region the records on major earthquakes are not enough to discuss the seasonal variation. But it is able to show that large earthquakes with magnitude 7.0 or over occurred more frequently from March to September in the inland regions where no effect of the major earthquakes on the Pacific coast is expected. It seems that the decrease in the weight of water on land and lowering of the mean sea level trigger the occurrence of major earthquake between the oceanic and continental plates, when the strain accumulates closely to the limit. It is also considered that the increase of ground water in the fault zone has an influence on the occurrence of large shocks inland in their critical states.View full abstractDownload PDF (1287K) -
Shozo MATSUMURA1982 Volume 35 Issue 1 Pages 65-75
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSA new parameter which characterizes the pattern of time sequence of earthquakes was derived based on the Weibull distribution. This parameter ν, which is closely related to apparent interaction between two successive earthquakes, represents the pattern of earthquake occurrence: ν=0.5 for random occurrence, and ν_??_0.5 for successive and periodical occurrences, respectively. It is expected that percursory seismicity change, if any, will effectively be detected by monitoring the ν-value.
The data of microearthquakes from July 1979 to November 1980 observed at the Iwatsuki Crustal Activity Observatory were examined by using the parameter ν, and the following results were obtained. The time sequence of microearthquakes shows a successive pattern in gross. The ν-value tends to deviate from the mean level before and after major earthquakes with magnitude equal to or greater than 4.0. A large drop of the value was observed before and after the largest earthquake (M=6.1, September 25, 1980, 02h 54m) investigated. The remarkable decrease in ν-value started about twenty days prior to the earthquake.View full abstractDownload PDF (847K) -
Hideo YUKUTAKE, Yoshihisa IIO, Ryohei NISHIDA, Keisuke TANIGUCHI, Tsut ...1982 Volume 35 Issue 1 Pages 77-90
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSThis paper is intended to find the microfracture occuring in the depths of the mine with a wide band frequency response up to higher than several handreds Hz. One of our purposes is to study the microfracture caused by disturbance of stress, for example, by blasting a rock with dynamite. The other one observes the ultramicroearthquake obtained with the highly sensitive observations in the depths of the mine. These purposes were performed at three mines, Sasare, Akenobe and Nakatatu.
The elastic waves with frequency of 600-700Hz and S-P time of 30-40msec were observed at Sasare mine, Ehime prefecture. Unfortunately, because this mine was closed down after a few weeks, we were not able to investigate in further details.
The observations were carried out for ten days at Akenobe mine, Hyogo prefecture. These series ended in failure.
Three sensors were set near the place where a rock is blasted with dynamite at Nakatatu mine, Fukui prefecture. We succeeded in finding out thousands of elastic wave of high frequancy, of which spectrums predominated with the main frequencies of few handreds Hz. These fractures occasionally accompanied with the swarm. Energy of each microfracture is evaluated to range from 103 to 105 erg. Magnitude calculated by simple formula is to range from -3 to -5. The forcal distance is found to range from 50m to 200m. It is reasonable to consider that these fractures were not caused by a sudden change in stress which happened by the blast of dynamite but by a phenomenon of a slow variation of stress.
These fracture phenomena treated in this paper are useful to be applicable to not only a rock experiment in laboratory but also the study of natural earthquake at field.View full abstractDownload PDF (3883K) -
Kinichiro KUSUNOSE, Osamu NISHIZAWA, Kaoru ONAI1982 Volume 35 Issue 1 Pages 91-102
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSHypocenters of AE in a rock under uniaxial compression test were determined. A local fracturing mechanism was investigated from variation of AE hypocenter distribution of before and after the local fracture. Just before a large AE is radiated from a local fracturing, an AE gap which is similar to seismic gap is observed. The large AE itself is followed by aftershock sequence. The large AE occurs at one end of the gap and the aftershock sequence occurs inside an area of the AE gap.
Focal mechanism solutions of AE, obtained from P-wave initial motion directions, show that the angle between the fault plane and the maximum stress axis of foreshock sequence is gentler than that of aftershock sequence. The solutions suggest that the cracks generating aftershock sequence propagate the unfractured gap between echelon type cracks generating sequencial foreshocks and link the echelon type cracks to form one of the main fracture planes.View full abstractDownload PDF (1056K) -
Yasuo TAKEHANA, Yoji KOBAYASHI, Hiroshi WAKITA, Yuji NAKAMURA1982 Volume 35 Issue 1 Pages 103-115
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSIn order to examine if the emission of hydrogen shows any correlation with movements of an active fault, we have measured the concentration of hydrogen in soil gas accumulated in holes along the Negoro fault, the Median Tectonic Line. Measurements were made at a newly formed outcrop at Bodai Pass, Wakayama, Japan. Significantly high H2 concentrations were observed for almost all measuring sites located either on or near the fault. The highest H2 concentration was 7600ppm, which is about 15, 000 times as high as that of the atmosphere. In order to obtain basic knowledge on the H2 emission through the Negoro fault, changes in H2 concentration of soil gas with time were measured intermittently at two measuring sites on the fault from the time of the initiation of storing soil gas to that of 30hrs later.
Areal distribution of sites with high concentration of H2 and temporal variations in H2 concentration in soil gas suggest that the observed H2 emission is clearly correlated with presence of the fault.View full abstractDownload PDF (1181K) -
Osamu Nishizawa, Kinichiro KUSUNOSE, Takashi YANAGIDANI, Fukashi OGUCH ...1982 Volume 35 Issue 1 Pages 117-132
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSStochastic process of the occurrence of AE events and their spatial distribution during creep in granite were studied. In the stage of steady creep, linear increments of volumetric and circumferential strains accompanied with a steady AE activity. A transition point from steady creep to tertiary creep estimated by the strain data agrees with that estimated by the change of AE activity. Frequency distribution of AE rate during steady creep shows Poisson distribution, according to X2-test with a significance level of 0.05. In the stage of tertiary creep, however, Poisson process of the occurrence of AE has disappeared. Spatial distributions of hypocenters exhibit concentration patterns during steady creep. The temporal randomness of the occurrence of AE events cannot always correspond to the spatial randomness. The present results suggest that the transition from steady creep to tertiary creep may be characterized by the occurrence of AE events with large amplitude, their aftershocks, change of stress distribution in the rock and migration of hypocenters. There seems to be a close relation between stochastic process of the occurrence of AE events and the manner of the AE emanation. Taking similarities between AE events and earthquakes into account, a study of stochastic process in microearthquake occurrence will play an important role for the earthquake prediction study.View full abstractDownload PDF (1446K) -
Kazuaki NAKAMURA1982 Volume 35 Issue 1 Pages 133-135
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (363K) -
Tetsuo TAKANAMI1982 Volume 35 Issue 1 Pages 135-139
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (578K) -
Kenji KANJO1982 Volume 35 Issue 1 Pages 139-142
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (584K) -
Akio YOSHIDA1982 Volume 35 Issue 1 Pages 142-144
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (363K) -
Kiyoo MOGI1982 Volume 35 Issue 1 Pages 145-148
Published: March 25, 1982
Released on J-STAGE: March 11, 2010
JOURNAL FREE ACCESSDownload PDF (506K)
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