巻号一覧
38 巻 (1985)
- 4 号 p. 485-
- 3 号 p. 315-
- 2 号 p. 159-
- 1 号 p. 1-
前身誌
38 巻, 2 号
選択された号の論文の12件中1～12を表示しています
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平田 隆幸, 柳谷 俊, 寺田 孚1985 年 38 巻 2 号 p. 159-172
発行日: 1985/06/25
公開日: 2010/03/11
ジャーナル フリーTime series of AE events during uniaxial creep in Ohshima granite were investigated. We determined both the origin time and the magnitude of AE events simultaneously by using the microcomputer equipped system. First, we analyzed the occurrence of AE events graphically. It is apparent that there were no aftershock sequences as observed in the occurrence of earthquakes. Second, we studied whether the occurrence of AE events is the Poisson process or not by taking into account of their magnitude. By plotting the exponential probability of time intervals between consecutive events, we were able to test it graphically. We also tested it by means of the χ2-test. The test shows that during the secondary creep the occurrence of AE events is the Poisson process unrelated to their magnitude. During the stage of tertiary creep, while the occurrence of large AE events was the Poisson process except when the catastrophe was imminent, the occurrence of smaller AE events began to deviate from the Poisson process. In order to predict forthcoming instability, we tried to analyze time-interval distribution of large AE events by plotting them on Weibull probability paper. This revealed that the AE occurrence changed from being random to being periodic just prior to the main fracture.抄録全体を表示PDF形式でダウンロード (1447K) -
加藤 完, 西澤 修, 楠瀬 勤一郎, 池田 喜代治1985 年 38 巻 2 号 p. 173-182
発行日: 1985/06/25
公開日: 2010/03/11
ジャーナル フリーIn order to understand mechanisms of radon accumulation in the soil gas around active faults and radon anomaly in groundwater or soil gas near epicenters before and after large earthquakes, we investigated variations of radon emanation from Westerly granites under uniaxial compression. Creep tests were carried out under multi-stress levels by increasing the stress stepwise and by applying constant stresses intermittently, to clarify the relations between stress, radon emanation, acoustic emission and strain.
The results of the experiments are as follows:
1) Accompanying acoustic emission, radon emanation began to increase around 140MPa of axial stress which corresponds to 70% of fracture stress (200MPa) of Westerly granite. Radon emanation increased over this stress, corresponding to every increase of axial stress. This suggests that gaseous radon appears outside the rock sample, passing through the channels formed by the network of stress-induced cracks inside the rock sample.
2) After the axial stress was removed, stressed rock samples that formerly showed increase of radon were still emanating the same amount of radon. This irreversible increase of radon emanation may indicate that the crack network remains inside the rock sample after removing the stress.
3) Remarkable increase of radon emanation appeard after the utimate fracture, which may be caused by increase of fracture surfaces and development of crack networks.
4) The α-ray intensity-time curves of the air around the rock sample indicated that most of radon consists of 220Rn (Thoron) by comparing the observed curves to the calculated curves for various initial ratios of 222Rn (Radon, 3.825 day half-life) and 220Rn (52 second half-life).
The above results indicating the strong relation between cracks and radon emanation suggest that high radon concentration around active faults may be caused by gaseous radon accumulation through the channels of dense networks of crack, joint and fault.抄録全体を表示PDF形式でダウンロード (1067K) -
地震発生機構における意義杉崎 隆一, 鈴木 和博, 大井 田徹, 山崎 文人1985 年 38 巻 2 号 p. 183-191
発行日: 1985/06/25
公開日: 2010/03/11
ジャーナル フリーFor the purpose of earthquake prediction, chemical compositions of bubble gases from a mineral spring have been successively measured since 1978. The spring is located close to Median Tectonic Line, the longest active fault in Japan. The gas contains helium as much as 300ppm. This suggests that the gas and the mineral water issuing from a fissure of Tertiary volcanics are derived from depths. Sometimes, hydrogen appears in the bubbles, while earthquake swarm occurs along an active fault which runs from WNW to ESE about 3km to the spring. Successive measurements showed that the period of H2 emission from the mineral spring coincided with that in which the earthquake swarm had been active. Four cases of the coincidence without exception were observed in the last three years. The range of the fluctuation of H2 concentration amounts to almost two orders of magnitude up to 200ppm, while other gases such as He, Ar, N2 and CH4 do not much fluctuate. The concentration of H2 correlates with the energy released by the seismic activity. This field evidence and laboratory experiments infer that H2 observed at the mineral spring is produced by a reaction between groundwater and rock fractured by seismic activities. Temporally, the H2 emission preceds the occurrence of the earthquake swarm. This suggests that microcracks in rocks occur prior to earthquakes and H2 is produced by the chemical reaction in the microcracks. This precursory emission of H2 may be useful for the prediction of earthquakes.抄録全体を表示PDF形式でダウンロード (3041K) -
山崎 文人, 大井 田徹1985 年 38 巻 2 号 p. 193-201
発行日: 1985/06/25
公開日: 2010/03/11
ジャーナル フリーThe Nagoya University seismograph telemetry network for microearthquake observation in the Chubu district, central Japan locates in the northeastern region of the subducting Philippine Sea plate. It is therefore valuable for a refined study on the descending plate. The data from April, 1978 through March, 1984 was used to delineate the seismic zone by depth-contours of the upper boundary, as shown in Fig. 10. The descending Philippine Sea plate beneath the Chubu district is devided into three slabs by the difference in dip angles and dip directions; These are named “Tonankai Slab”, “Tokai Slab” and “Suruga Slab”, respectively. The geometry of these slabs seems to be related with the seismic regionality suggested by UTSU (1977) for the historical great earthquakes along the Nankai trough.抄録全体を表示PDF形式でダウンロード (1097K) -
梅田 康弘1985 年 38 巻 2 号 p. 203-215
発行日: 1985/06/25
公開日: 2010/03/11
ジャーナル フリーThe detail surveys in the source regions of large shallow earthquakes clearly show that there is a particular region characterized by a large dislocation, large acceleration and extremely low aftershock activity. The predominant short period waves, namely high energy seismic waves, are radiated from this specific region called “an earthquake core” which occupies a little portion of main fault. Shortly before these high energy waves, an acceleration phase is detected on the broad-band seismograms.
The near field shear strain waves radiated by a faulting are calculated. When the maximum strain excited by shear waves exceeds the critical strain at some points in the source region, it is possible to make start new faulting. In such a case, an earthquake core as a multiple rupture region is produced in the vicinity of the faulting direction.
Shear strain excitation caused by the strain waves goes ahead of the front of the initial fault, because the wave velocity is usually greater than the rupture velocity. The dislocation and rupture velocity of new faults are always greater than those of initial fault. This phenomenon is called “an acceleration of faulting”.抄録全体を表示PDF形式でダウンロード (1536K) -
出射 隆文, 堀家 正則, 岩田 知孝1985 年 38 巻 2 号 p. 217-232
発行日: 1985/06/25
公開日: 2010/03/11
ジャーナル フリーWe have investigated the characteristics of S coda waves on a sedimentary basin for examining if they may be applicable to estimate the stable amplification factor. The results are as follows: (1) R. M. S. amplitude ratios of coda waves observed on the basin to coda waves on the nearest rock site were inconsistednt with the ratios of S waves between the above two sites for frequecies lower than 3Hz. The ratios of coda waves scattered as much as those of S waves. (2) The phase velocities determined for coda waves on the basin were consistent with those of Rayleigh waves estimated by another study. (3) Comparing coda waves observed on the basin with those synthesized through convolving the SH wave response for the basin and the seismogram on the rock site, the former was much smaller than the latter. From the above three results, coda waves on the basin seem to consist of not only single-scattering S waves but also surface waves generated locally. It is therefore difficult to estimate reliable amplification factor from coda waves observed on the sedimentary basin.抄録全体を表示PDF形式でダウンロード (1507K) -
小山 順二, 島田 伸介1985 年 38 巻 2 号 p. 233-241
発行日: 1985/06/25
公開日: 2010/03/11
ジャーナル フリーA relation between surface-wave magnitude Ms and fault area S for great earthquakes has been proposed;
logS≈2Ms-11.5 (Ms>7.5).
A similar formula has been also derived for body-wave magnitude mb* redetermined from maximum amplitudes of short-period P-wave trains;
logS∝1.7mb*.
These are quite different from a theoretical relation expected on the basis of long wave approximation. The statistical theory of extreme values has been applied to understand the relations considering that the component waves which consititute the wave trains for mb*-Ms determinations originate from the random fracture of fault heterogeneities.抄録全体を表示PDF形式でダウンロード (935K) -
三田市西部での最終活動西村 進, 茂木 透, 見野 和夫, 山田 治1985 年 38 巻 2 号 p. 243-249
発行日: 1985/06/25
公開日: 2010/03/11
ジャーナル フリーNormal and reversed faults are observed at the outcrops of the western part of Sanda City, Hyogo Prefecture. Normal faults which are observed along the Sanda-Yamasaki tectonic line are discordant with the stress e stimated by the character of earthquakes. The results of the measurements of the crustal stress and the mechanism of the micro-earthquakes around these area indicate that the horizontal compressive stress acts in E-W direction around this region. This discordance is solved by the observation of a new outcrops in the western part of Sanda City, where that ground is prepared for housing. The movement of a fault, concealed underground, brings about various kinds of breaks on the loose sedimental layer.
The magnitude of earthquake occurred around here is estimated as about 7. The age of faulting is also estimated by 14C dating younger than 3340 years old and by the rice field older than 400 years old. This falt might be occurred Harima Earthquake in AD 868.抄録全体を表示PDF形式でダウンロード (4468K) -
濱松 音藏, 橋本 萬平1985 年 38 巻 2 号 p. 251-257
発行日: 1985/06/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (536K) -
藤原 健治, 瀬野 徹三1985 年 38 巻 2 号 p. 259-261
発行日: 1985/06/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (406K) -
茂木 清夫1985 年 38 巻 2 号 p. 262-265
発行日: 1985/06/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (517K) -
石川 有三1985 年 38 巻 2 号 p. 265-269
発行日: 1985/06/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (558K)
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