巻号一覧
44 巻 (1991)
- 4 号 p. 271-
- 3 号 p. 155-
- 2 号 p. 63-
- 1 号 p. 1-
- Supplement 号 p. 3-
前身誌
44 巻, 2 号
選択された号の論文の10件中1～10を表示しています
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角田 寿喜, 宮町 宏樹, 高木 章雄1991 年 44 巻 2 号 p. 63-74
発行日: 1991/06/24
公開日: 2010/03/11
ジャーナル フリーSeismic activities are investigated in detail for intermediate depth events in a northern part of the Kyushu-Ryukyu arc using seismic data observed at stations of Kagoshima University (KGU) and Fukuoka Meteorological Observatory (FMO): high sensitive KGU stations are effective in reducing errors especially in focal depth and epicenter longitude for events in south Kyushu. On the northeastern side of the Kirishima volcanoes, some relatively large events occurred in a nearly vertical narrow zone at depths from 80km to 120km through the deep seismic plane dipping at a high angle. Possible focal mechanisms suggested thrust faulting with a tension axis dipping steeply but could not always be interpreted as down-dip extension. Considerable activities were also observed at depths from 120km to 180km through the seismic plane under the Kaimon-lake volcano and a chain of events branching off from the cluster continues north-northeastward to a depth of 100km under the Sakurajima volcano. The events in the chain showed repeatedly a tendency to migrate from the cluster zone toward the volcano. It is quite plausible that these seismic activities through the seismic plane are associated with the supply of volcanic energy in Kyushu.
Seismicity gaps traversing obliquely through the deep seismic plane are especially noticeable under the geologically young calderas, namely, Aso and Aira: intermediate earthquakes also rarely occur under the Ata caldera. Considering large discontinuities speculated in the seismic plane in Kyushu as well as prominent recent structures transverse to the arc, the seismicity gap is supposedly formed in a narrow zone of rather high temperature including such a discontinuity segmenting the seismic plane.抄録全体を表示PDF形式でダウンロード (1980K) -
川崎 一朗, 大嶋 主悦, 三上 直也, 堀 貞喜1991 年 44 巻 2 号 p. 75-83
発行日: 1991/06/24
公開日: 2010/03/11
ジャーナル フリーThis is a preliminary report on an attempt to detect silent and slow earthquakes that are supposed to occur around Japan Islands between the Eurasian and the subducting Pacific plates, where inter-plate seismic coupling is 0.2-0.3. In the first step, we have obtained high-pass filtered strain with a cut-off period of 7 hours from the quartz-pipe extensometer records (sampling interval is 5min) of Matsushiro Seismological Observatory of Japan Meteorological Agency for a period from July 1988 to November 1989. When we have found a signal of a pulse width of -10min to -1 hour above a noise level of 10-9 in the high-pass filtered strain, we have calculated spectrum by the Maximum Entropy Method of the quartz-pipe extensometer seismograms (sampling interval is 0.2s) of an 48 hour length. For days when eigenperiods of Earth's free oscillations have been found in the spectrum by the Maximum Entropy Method, we have calculated Sompi-spectrum of IDA long period records, where we could not identify any eigenperiods of spheroidal oscillations of periods longer than 500s. We thus could not find silent and slow earthquakes for the period around Japan Islands with the above tactics.抄録全体を表示PDF形式でダウンロード (1194K) -
羽鳥 徳太郎1991 年 44 巻 2 号 p. 85-91
発行日: 1991/06/24
公開日: 2010/03/11
ジャーナル フリーAccompanied with the Mariana Trench earthquake (epicenter: 15.226°N, 147.529°E, d=32km, Ms=7.5, USGS) of April 6, 1990, a tsunami was observed at many tidal stations in Japan. The travel times at these stations were about 3 hours, and the maximum wave at each station was observed at the time about 2 hours later than the initial wave. The average double-amplitude was about 20cm, but the amplitudes at Muroto and Tosa-Shimizu near the tip of peninsula reached 40cm with the wave period of 8 minutes. Judging from the diagram of the attenuation of wave-height with distance, the tsunami magnitude on the Imamura-Iida scale was determined to be m=2. This value is one grade (5 times for wave energy) high for an earthquake having a magnitude of Ms=7.5. Though the energy concentrated in Japan by the effect of submarine topography, the tsunami might be generated by a high-angle thrust fault.抄録全体を表示PDF形式でダウンロード (718K) -
岡田 成幸, 鏡味 洋史1991 年 44 巻 2 号 p. 93-108
発行日: 1991/06/24
公開日: 2010/03/11
ジャーナル フリーFor correctly evaluating the future earthquake damage done to the regional elements at risk, it is neccessary to assess vulnerability describing the level of loss that would be caused to element or percentage of element damaged in the area as a result of experiencing earthquake ground motion of a certain severity. The purpose of this paper is to develop inventory vulnerability functions for evaluating earthquake damege in Japan.
To develop serviceable vulnerability functions for all the existing elements in Japan, we tried to translate the descriptions in the expounder of the intensity scale of the Japan Meteorological Agency (JMA) reported by the Tokyo Metropolitan Government Disaster Prevention Council into the functional equations on vulnerability. First, quantitative data were made from the expounder qualitatively expressing damage phenomena by introducing the percentile values equivalent to the adjective and adverb expressions on the scale of degree of damage within the descriptions. Second, vulnerability equations were derived from the quantitative data by means of the least squares method. We introduced a simple model in which the vulnerability characteristics of an element was expressed by a normal distribution function in terms of the seismic intensity on the JMA scale.
By follwing the above method we derived the inventory vulnerability functions for 56 kinds of elements; e. g., inhabitants, buildings of various kinds of construction, building contents, bridges, roadways, and lifelines. These functions agreed well with the damage data obtained in the past earthquakes. As an example of applying the assessed functions to damage evaluation, the probability that an inhabitant suffers injuries due to objects fallen or furniture overturned during an earthquake was evaluated by considering both functions on vulnerability of furniture and on ability of human behavior to evacuate. A group of these equations should be useful for total damage evaluation.抄録全体を表示PDF形式でダウンロード (2053K) -
横井 俊明, 入倉 孝次郎1991 年 44 巻 2 号 p. 109-122
発行日: 1991/06/24
公開日: 2010/03/11
ジャーナル フリーWe show an example of application of the waveform synthesis by the empirical Green's function technique based on the scaling law of the source spectra, in order to study source process. First, the relation of the ratios of source parameters (such as crack radius and local stressdrop), between small and large earthquakes, with the spectral ratio of the observed ground motion, are derived from the idea of multicrack model, in which subevents are composed of circular cracks obeying the ω-2-scaling law. Then, the accelerograms of the second (M=6.1) and the third (M=6.0) largest aftershocks of the 1983 Japan Sea earthquake are synthesized, from a smaller event (M=5.0, 3.9) occurring in the same source region, in order to obtain the optimum value of the parameters used in the synthesis. In the case of the second largest event, the synthetic waveform and its spectra obtained by the formula for the single crack event, are successfully fit to the observed ones. In contrast, it's necessary, for the synthesis of the third largest event, to employ the formula for the multi-crack event. It's suggested by the source parameters, such as stress drop and crack radius, obtained from the observed spectral ratio. The used values of the parameters in synthesis make us guess such a complicated source process as relatively large crack with low-stress drop associated by small crack with high-stress drop.抄録全体を表示PDF形式でダウンロード (1806K) -
渡辺 偉夫1991 年 44 巻 2 号 p. 123-129
発行日: 1991/06/24
公開日: 2010/03/11
ジャーナル フリーThe Hanai's diary at Wakuya, the north part of Miyagi Prefecture, Tohoku District, Japan, is the records on natural phenomena from November 30, 1833 to January 1, 1848. The contents of diary are mainly the weather, moreover, the diary records eighty earthquakes. From annual number of earthquakes, there are two periods of high seismic activity of a few years from 1835 and 1841. Two disaster earthquakes with the seismic intensity V-VI occurred in July 20, 1835 and January 19, 1841. From the intensity distribution, the epicenter of the 1835 earthquake is deduced to be near that of the 1978 Miyagiken-oki earthquake. The disaster and liquefaction areas of ground produced by the former earthquake were larger than those of the latter one. The magnitude of former earthquake was thus presumed to be 7.5. The 1841 earthquake produced the disaster only at Wakuya and had no aftershocks. From these facts and the seismic intensity distribution, the earthquake is thought to occur off Miyagi Prefecture. We classify the earthquake into so called ‘Kinkasan-oki type’ and estimate the magnitude at 7.1. This magnitude is the same as that of the 1937 earthquake.抄録全体を表示PDF形式でダウンロード (887K) -
浅野 周三, 角田 智彦, 平間 邦興, 桑原 徹, 安井 譲, 井川 猛, 黒田 徹, 高橋 明久, 足立 幾久, 仁平 孝夫1991 年 44 巻 2 号 p. 131-143
発行日: 1991/06/24
公開日: 2010/03/11
ジャーナル フリーThe survey of the underground structure to a depth deeper than 1km was conducted with the seismic reflection method in the Tokyo Metropolitan area in July, 1989. This is a feasibility study to look for how to obtain a detailed underground structure above the seismic basement under the Tokyo Metropolitan area from the view point of natural hazard reduction study. The profile in Kiyose, the most northern part of Tokyo Metropolis, has a length of about 1000m. The hydraulic weight (200kg) dropping device, “Yuatu Impactor”, which was developped by the JAPEX Geoscience Institute, Inc., was used as a source. Both intervals of shots and receivers were 10m. At each shot point, signals of ten shots were stacked and a linear array of 12 (9) geophones with a natural frequency of 10 (28) Hz was used at each receiving point. Through the conventional digital processing, the following results were obtained:
(1) Except for the very thin surface layers, six major reflecting horizons were identified, and the P wave interval velocity is 1.6, 1.7, 1.8, 1.9, 2.2, 2.7km/s in each layer from top to down. The deepest horizon is at a depth of about 1600m, which is the deepest horizon ever detected by the reflection method with non explosive sources in the Kanto Plain. The layers, especially deep ones, have a tendency inclining to the east. The reflection, however, was not observed from the top of the basement with a P wave velocity of about 5km/s.
(2) The underground structure derived is qualitatively correlated to the geology revealed by a well with a depth of 800m near the profile.
The results show the usefulness of reflection profiling with non explosive sources like Yuatsu Impactor in sediment-covered and populated areas.抄録全体を表示PDF形式でダウンロード (2554K) -
阿部 勝征1991 年 44 巻 2 号 p. 145-146
発行日: 1991/06/24
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (273K) -
静岡市付近の地震活動への適用前田 憲二, 吉田 明夫1991 年 44 巻 2 号 p. 147-150
発行日: 1991/06/24
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (464K) -
植竹 富一, 真下 貢, 天池 文男1991 年 44 巻 2 号 p. 151-154
発行日: 1991/06/24
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (522K)
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