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44 巻, 1 号
選択された号の論文の9件中1～9を表示しています
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―5衛星運航下における基線決定の再現性―木股 文昭, 中村 勝, 宮島 力雄, 奥田 隆, 里村 幹夫, 臼井 和平, 佐々木 祐治, 佐々木 嘉三1991 年 44 巻 1 号 p. 1-7
発行日: 1991/03/24
公開日: 2010/03/11
ジャーナル フリーThe three-hours GPS observation by Trimble 4000 SD receivers was repeated at five stations in central Japan every day during four weeks from February 25, 1990. Data obtained from five satellites could achieve good results 2-4 times better than previous works with four satellites. The standard deviations of baseline lengths, namely the day-to-day repeatabilities, by the the triple difference technique were 0.11-0.48ppm for all of ten baselines ranging from 22km to 172km. However, those of eight baselines longer than 40km show less than 0.2ppm. The double difference technique applied to the shortest baseline (Nagoya-Inuyama, 22km) data too. This could improve the standard deviation from 7mm (0.31ppm) to 4mm (0.17ppm). The GPS observation under five satellites utilization maintains the same precision precision as electro-optical distance measurements (EDM), even for a few tens-kilometer baseline.抄録全体を表示PDF形式でダウンロード (997K) -
横浜市舞岡発破および大黒発破による人工地震波の解析山中 浩明, 瀬尾 和大, 佐間野 隆憲1991 年 44 巻 1 号 p. 9-20
発行日: 1991/03/24
公開日: 2010/03/11
ジャーナル フリーThe seismic refraction survey was conducted in the southwestern part of the Tokyo Metropolitan area to make clear the deep sedimentary structure. Two explosions were made at Daikoku and Maioka in Yokohama city in 1988, and the resultant seismic waves were observed at 83 temporary observation sites along four surveying lines:
a) Yumenoshima to Enoshima,
b) Daikoku to Nagatsuta,
c) Nagatsuta to Kanazawa, and
d) around Takatsu.
The travel time analysis for the above data and additional data from previous explosions in the area for reference has been made.
The followings were our conclusions:
1) The subsurface structure consists of five layers characterized by P-wave velocities of 1.8, 2.3, 2.9, 4.7 and 5.5km/s. The top layer with a P-wave velocity of 1.8km/s disappears around Enoshima. The layer with a P-wave velocity of 5.5km/s could not be confirmed for the southwestward area.
2) The topography of the layer with a P-wave velocity of 4.7km/s forms a synclined structure having its maximum depth of more than 4km between the Maioka and Daikoku explosion sites. The depth to this layer becomes drastically shallower toward Enoshima.
3) The step-like topography of the layer with a P-wave velocity of 5.5km/s, which has been found in the previous study, could not be confirmed, because of low S/N ratios of the observed seismograms.抄録全体を表示PDF形式でダウンロード (1586K) -
浅田 照行, 小泉 尚嗣, 松尾 成光, 西村 進1991 年 44 巻 1 号 p. 21-28
発行日: 1991/03/24
公開日: 2010/03/11
ジャーナル フリーAn earthquake, whose magnitude was 4.9, occurred in the southern part of Lake Biwa on January 11, 1990. The epicenter of it was just near Moriyama observation well, where we continuously measured many geochemical and hydrological parameters for earthquake prediction research from April, 1983. These data were carefully compared with the water level data of Lake Biwa and the meteorological factors to check any possible relationship. We concluded that nothing but the groundwater temperature at a depth of 780m anomalously changed before the earthquake.抄録全体を表示PDF形式でダウンロード (826K) -
森 俊雄1991 年 44 巻 1 号 p. 29-37
発行日: 1991/03/24
公開日: 2010/03/11
ジャーナル フリーWe have been observing geoelectric field in land using the facilities of NTT corporation and on the ocean-floor using the ocean bottom seismograph observation systems of JMA, in the cenral part of Japan. By these observations we obtain highly stable data compared with those by ordinary observations. Some anomalous changes preceding earthquakes and volcanic eruptions were detected by simple methods. However, we still do not have general concepts about the anomalous changes in the electric fields as precursors of tectonic activities, that is, when, how long, how much intense and what type.
In order to improve the detectability of anomalous changes and automatically detect the precursory signals generated by seismic or volcanic activities in real-time or in quasi-real-time, we need to eliminate the effects of external geomagnetic changes and the motion of sea water. I have proposed that the induced electric fields in land and on the ocean-floor are expressed by a stochastic difference equation using the associated data such as the magnetic fields and/or sea level. The parameters of the equation are determined so as to minimize the AIC (Akaike Information Criterion).
In this study, I apply above method to the various electrical records from January to September, 1989. In the case of the electric fields at Mito-group, induced electric fields such as daily variations and telluric storms can be calcurated using the magnetic variations, and are considerably eliminated from the observed field. Then the degree of improvement in detecting anomalous electrical variations at the Mito-group is 5-10 times using X, Y and Z components of magnetic field. One at the Numazu-group is about 5 times using X and Y, and one on the ocean-floor is about 10 times using X, Y and sea level. In these cases, practically, the determined parameters were applicable for few months.抄録全体を表示PDF形式でダウンロード (1220K) -
堀 修一郎, 長谷川 昭1991 年 44 巻 1 号 p. 39-48
発行日: 1991/03/24
公開日: 2010/03/11
ジャーナル フリーA sharp impulsive phase following direct S is found in seismograms of an earthquake swarm that occurred beneath Mt. Moriyoshi, northern Akita Prefecture. This phase is most clearlyy defined on horizontal component instruments and is identified as SxS reflection from a sharp velocity discontinuity in the mid-crust. Reflected and S-to-P converted phase (SxP reflection) at the discontinuity is also detected on vertical component seismograms at station NIB, although its amplitude is not very large. The large amplitude of the SxS phase and the ratio of SxS to SxP amplitudes are explained by a large velocity contrast across the dicontinuity, such as an upper surface of magma body.
We try to map this velocity discontinuity by analyzing observed arrival times of the SxS phase. The result shows that this unusual S-wave reflector is distributed over an area of 15×15km2 at depths ranging 12-17km beneath Mt. Moriyoshi, a Quaternary volcano. It becomes shallow at an angle of about 15° toward the east-southeast, in which direction more active volcanoes are densely distributed. Beneath the presently mapped S-wave reflector, anomalously deep low-frequency microearthquakes, perhaps caused by magmatic activity, are occurring at depths ranging 27-37km. It is found that the S-wave reflector and the deep low-frequency events are located around a low-V zone of P-wave existing in the crust and the upper mantle beneath active volcanoes抄録全体を表示PDF形式でダウンロード (1432K) -
石井 紘1991 年 44 巻 1 号 p. 49-52
発行日: 1991/03/24
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (531K) -
吉田 満, 川崎 一朗1991 年 44 巻 1 号 p. 53-57
発行日: 1991/03/24
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (525K) -
中根 勝見, 藤井 陽一郎1991 年 44 巻 1 号 p. 59-60
発行日: 1991/03/24
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (249K) -
岡田 義光1991 年 44 巻 1 号 p. 61-62
発行日: 1991/03/24
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (1340K)
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