巻号一覧
39 巻 (1986)
- 4 号 p. 525-
- 3 号 p. 351-
- 2 号 p. 201-
- 1 号 p. 1-
前身誌
39 巻, 4 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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梛原 誠一, 鈴木 茂文, 房 律子, 木下 肇1986 年 39 巻 4 号 p. 525-532
発行日: 1986/12/25
公開日: 2010/03/11
ジャーナル フリーThe design and use of a newly developed marine heat flow measuring system is described. It has as much as 16 temperature sensors (thermistors) and can record the data sequentially for about 30 hours. Each set of data consists of 16 pairs of pulses; the first 4 for the header bits and the rest 12 bits are assigned to the temperature value. The data are recorded on a magnetic cassette tape recorder. The system carries a modified needle probe to detect insitu thermal conductivity by applying a heating pulse of 8sec long. We carried out a series of measurements at Sea of Japan to test a reliability of the system, using a modified 6-channel (reduced from 16) probe. The temperature profiles obtained on the deep sea floor (Sea of Japan) showed a good quality.抄録全体を表示PDF形式でダウンロード (3473K) -
南島 正重, 山崎 謙介, 工藤 一嘉1986 年 39 巻 4 号 p. 533-554
発行日: 1986/12/25
公開日: 2010/03/11
ジャーナル フリーIn order to make clear the effects of sedimentary layer on strong ground motion due to earthquakes, a tripartite array with strong-motion accelerographs of three orthogonal components has been deployed since 1982 in the campus of Tokyo Gakugei University, Koganei, Tokyo. The array is located at the western suburbs of the Tokyo Metropolis on Pleistocene sedimentary layer which reaches ca. 2000m depth overlying Pre-Tertiary basement. Digital accelerographs with sampling rate of 60Hz and with 12bits/word are installed on the array of 300-400m sides.
Several events among all the data acquired by the present time are available for analyses; those are in the magnitude range of 5.7-7.3, in the depth range of 20-400km and in the range of epicentral distance of 47-340km. Although the maximum height and the phase of high frequency acceleration are strongly affected by variety of surficial portions (thickness_??_10m) underlying the foundations of seismographs, ground velocity and ground displacement of each station of the array show coherent signals with same amplitude but poorly discriminated phase lag each other up to the coda of the raw wave trains. However, filtrated waves of the raw data through some narrow pass bands exhibit clearly discriminated phase lags among the three stations throughout the wave trains right after the S-wave onset.
Method of sums and the Fourier's analysis are adopted to derive apparent velocities of the later phases which are of considerable amplitude in ground displacement and ground velocity; the frequency range of the phases is 0.2-1.0Hz within which the velocity spectrum is in fairly high level. The results can be interpreted as surface waves excited in the thick sedimentary layer which covers the Tokyo area. Though the frequency dependence of phase velocity is clearly seen, it could not be confidently interpreted as a branch of unified single mode of surface wave. It is more likely to be interpreted as some branches of higher modes.
A moving-window analysis with multiple filtering technique has given time-varying frequency spectrum of the strong-ground motion wave trains. It also shows a sequence of average group velocities between seismic foci and the array station. The results in conjunction with those of the phase velocity suggest laterally heterogeneous surface layer in and around the Tokyo area.抄録全体を表示PDF形式でダウンロード (2350K) -
前田 直樹1986 年 39 巻 4 号 p. 555-566
発行日: 1986/12/25
公開日: 2010/03/11
ジャーナル フリーA method for automatic reading of phase times from seismic wave data developed by MAEDA (1985) was put into operation in the automatic seismic data processing system at Regional Center for Earthquake Prediction, Faculty of Science, Kyoto University [WATANABE et al. (1982)]. In this study, the data obtained by the automatic processing are compared with those by the off-line processing (manual reading) in order to see the reliability of the method for automatic reading.
The results are as follows: (1) About 90 percent of the differences between respective P times determined by the two processing falls in the range from -0.05s to 0.05s. (2) The second-order moment around zero of the differences between respective S times is 0.262(s2). (3) About 90 percent of the distances between respective epicenters and between respective hypocenters fall within 2.5km and 3.5km, respectively. (4) As to the ability of the automatic processing to read P times, the automatic processing can not pick as weak P onsets as the off-line processing can. But the difference of the detection capability is not so large. It is estimated as 0.36 in magnitude scale on average.
As mentioned above, it is verified that the automatic processing system, which uses the method developed by MAEDA (1985), attains the aim to offer the reliable seismic information.抄録全体を表示PDF形式でダウンロード (1148K) -
鯖江断層見野 和夫1986 年 39 巻 4 号 p. 567-577
発行日: 1986/12/25
公開日: 2010/03/11
ジャーナル フリーWe investigated the Sabae fault which runs from north to south in the central part of the Takefu·Sabae basin, Fukui Prefecture.
The Sabae fault is an active fault because there were two large and disastrous earthquakes in 1639 and 1900 which have M over than 6.0. After the result observed by the Hokuriku Microearthquake Observatory, the seismic activity in recent years is very low in the area of the Sabae fault.
The fault scarp can be observed along the east side of the Sabae plateau. It is inferred from the strike that the fault strike is NS or N10°W. Along the fault scarp, springs well or dry up. The alignment of these springs coincides with the fault trace. The length of the fault is estimated about 20km from the alignment of the springs and lineament of ground feature.
For the confirmation in existence of the fault, γ-ray surveys were carried out along the several routes across the fault. The multichannel analyser with Na (TI) scintillation counter (called MCA) was used in the survey. Increase of γ radiation due to 214Bi is clearly attributed to the radioactive decay of gaseous 222Rn emanating through the fault zone.
In the southern part of the Hokuriku district, large and disastrous earthquakes have been occurred in these 300 years such as the Nobi earthquake in 1891 and the Fukui earthquake in 1948. Therefore, the levelling surveys by the Geographycal Survey Institute were carried out several times along the route across the babae fault during a period from 1890 to 1948. The results of the surveys revealed that this basin is composed of three blocks. The block of the east side of the fault took place larger movement than the western block including the Sabae plateau. The different pattern between two blocks is due to existence of the Sabae fault.抄録全体を表示PDF形式でダウンロード (1180K) -
岩田 知孝, 入倉 孝次郎1986 年 39 巻 4 号 p. 579-593
発行日: 1986/12/25
公開日: 2010/03/11
ジャーナル フリーWe try to separate source effects, propagation path effects and site effects from observed S-waves in frequency domain. Assuming that an observed seismic spectrum is a combination of the source spectrum, the path effect in connection with the geometrical spreading factor and the anelasticity (Q-value) and the site amplification, we can construct the simultaneous logarithmic equations with the unknown quantities such as the source spectrum, Q-value and the site amplification. To solve these equations with linear inversion methods, we set up the criterion that the site effects have a factor of more than 2 due to the free surface amplification. This method is examined by using two data sets; one obtained from 1983 Japan-Sea earthquake (M=7.7) and its largest aftershock (M=7.1) at 6 stations and the other, its 10 aftershocks (M=4.0-6.1) at 3 stations, with hypocentral distances 80-250km and 70-150km, respectively. Only one station (TUC) is common to two data sets. Obtained Q-values of S-waves are propotional to the 0.6 power of frequency in the range of 0.5-8.0Hz. Site effects at TUC from the two independent data set agree well within each standard deviation. From the obtained source spectra, we determine the flat levels of displacement spectra, those of acceleration spectra and the corner frequencies, and then, estimate the seismic moment, crack radius and stress drop of every event.抄録全体を表示PDF形式でダウンロード (1826K) -
井田 喜明, 山口 勝, 増谷 文雄1986 年 39 巻 4 号 p. 595-605
発行日: 1986/12/25
公開日: 2010/03/11
ジャーナル フリーThe nature of recent seismicity was studied in the area of Kirishima volcano and Kakuto caldera, based on the data obtained through the permanent seismometrical network of Kirishima Volcano Observatory. Since September, 1983, a group of earthquakes with linearly aligning epicenters have been occurred north to south across the northern rim of Kakuto caldera. These events were accompanied by another group of linear epicenter distribution near Iino in the eastern part of the caldera. Before and after the initiation of these events, the pattern of seismicity changed significantly in the entire Kirishima and Kakuto area. Namely the epicenters tend to be more scattered before, but more concentrated in some special parts after. The linear alignments of epicenters in the caldera rim, Iino and some other locations intersect at a point near Ebino that has intense fumarolic zones and hot springs. Some epicenters also form arcs with the same centers as these radial alignments. Such distribution of epicenters in lines and arcs may be interpreted by an increase of magma pressure at a depth of about 10km beneath Ebino.抄録全体を表示PDF形式でダウンロード (1091K) -
黒川-岡津測線および長津田測線の地下構造山中 浩明, 瀬尾 和大, 佐間野 隆憲, 翠川 三郎1986 年 39 巻 4 号 p. 607-620
発行日: 1986/12/25
公開日: 2010/03/11
ジャーナル フリーThe seismic refraction prospecting was carried out in the southwestern part of the Tokyo Metropolitan area, to clarify the deep underground structure down to uppermost layer of the Earth's crust. The explosions were denoted at Nagatsuta, Kurokawa, Okazu and Yumenoshima. The explosion at Nagatsuta was planned to make clear the existence of vertical discontinuity of the basement between Nagatsuta and Yumenoshima, which has been suggested from the observation of Yumenoshima explosion. The underground structure was revealed by the travel time analysis. The main features of the underground structure are as follows:
1) The underground structure consists of 4 layers. The P wave velocities of these layers are 1.8 to 2.0, 2.9, 4.8 and 5.5km/s, respectively.
2) The thickness of the third leyer is several kilometers in this area, however this layer doesn't exist in the central part of the Kanto plain.
3) The first layer is thinner than the second one in contrast with the underground structure of Yumenoshima situated on the center of the Kanto plain.
4) The vertical discontinuity of the basement was not confirmed from Nagatsuta explosion, because the refracted wave from the basement was not observed as an initial motion at the expected stations.抄録全体を表示PDF形式でダウンロード (1685K) -
岩田 孝仁, 浜田 信生1986 年 39 巻 4 号 p. 621-634
発行日: 1986/12/25
公開日: 2010/03/11
ジャーナル フリーIn the present study, we have accumulated most complete seismological data and reinvestigated the seismicity associated with the 1944 Tonankai earthquake. Because of poor observation and social difficulty during the World War II, incompleteness and insufficiency in observational data resulted in rather obscure view about the actual process and mechanism of the earthquake. Number of aftershocks and their location accuracy reported by existing studies seem to be dissatisfactory for detailed discussion.
We found some observational data that are still available but have not been used yet, then, we applied a modern hypocenter location method to the newly compiled data and succeeded in increasing the number of accurately located aftershocks more than twice. The followings are important findings of the study.
The mainshock initiated from the bottom of the fault plane, in the south-west corner of the focal region. This feature is in accordance with the results of some previous studies. Most of aftershocks concentrated in the vicinity of the Shima spur, which extends south-east from the Shima peninsula to the Nankai trough. Temporal broadening of the aftershock region toward south-east along the spur is recognized and this trend seems to continue over 40 years until now. Distribution of aftershocks around Shionomisaki, the southern top of the Kii peninsula, may suggest some overlapping of the focal regions of the Tonankai and the 1946 Nankaido earthquake. Aftershock activity or induced seismicity is also recognized in the middle part of Shizuoka prefecture where some seismologists assume the focal region of a future interplate earthquake, so called Tokai earthquake. Seismicity around the southern Izu peninsula may represent an induced activity along one of the active faults which strikes southeast from the peninsula. Other induced seismic activity in inland area of central Honshu indicates a large extent of the effect of the interplate earthquake on the tectonic environment of the mentioned area. This study will contribute to gain better understanding of the process and mechanism of the Tonankai earthquake.抄録全体を表示PDF形式でダウンロード (1785K) -
野田 弘, 尾池 和夫1986 年 39 巻 4 号 p. 635-643
発行日: 1986/12/25
公開日: 2010/03/11
ジャーナル フリーVariations of the level of ground water were observed at four stations near the epicenter of the shallow earthquake (M4.6) which occurred in the southern part of the Lake Biwa which has been recently a low seismicity region.
About ten days before the occurrence of the earthquake anomalous changes of the water level were observed. Considering the relation between the variation of water level and rainfall in the ordinary period these anomalous changes were precursors of the earthquake.
Co-seismic steps of the water level were observed at two stations. One of them was a sudden ascent which was observed at the region where initial P motions were compressional. At another station which was in the dilatational P region sudden descents were recorded.
Such characteristic variations of the ground water level are detectable by using deep wells when an earthquake occur conspicuously in the low seismicity region, even if its magnitude is small.抄録全体を表示PDF形式でダウンロード (803K) -
1984年長野県西部地震の余震飯尾 能久1986 年 39 巻 4 号 p. 645-652
発行日: 1986/12/25
公開日: 2010/03/11
ジャーナル フリーWe observed ultramicroearthquakes with a magnitude (J. M. A. scale) down to -3, by the highly sentitive aftershock observation of the Western Nagano Prefecture Earthquake of Sep. 14, 1984 (M=6.8).
The seismometer used is a 2Hz velocity-type transducer with flat response up to about 1kHz. Signals were recorded continuously on an analog data recorder. The overall frequency response of the observation system is flat from 2 to about 270Hz (-3dB point). Its highest sensitivity for the ground velocity was 18300V/(cm/s).
About 10, 000 earthquakes were recorded for the period of the observation. From them, the shocks of which S-P times <0.6s were chosen and analyzed. The total number of the earthquakes analyzed is 183. Their frequency-magnitude distribution and frequency-S-P time distribution were investigated. The earthquakes analyzed are distributed in magnitude down to -3. Their S-P times are distributed down to 0.05s.抄録全体を表示PDF形式でダウンロード (732K) -
寒川 旭1986 年 39 巻 4 号 p. 653-663
発行日: 1986/12/25
公開日: 2010/03/11
ジャーナル フリーIn the evening of June 29, 1799, a strong earthquake occurred in an area which is presently a part of the Kanazawa City. The damage and its location are thoroughly described in old documents. The Kanazawa Castle was severely damaged. Stone wall collapsed and warped in many places. Small vertical displacement occured on the ground in front of the Ishikawa Gate. In the city, Ohtesaki, Ohmi-cho, Hikoso-machi, Misogura-cho, Kotatsuno, Utatsu-cho and Ohhi-machi were severely damaged. In these areas, the intensity of the shock is inferred to be of the order of VI-VII. Many stone lanterns jumped up nearly 2m, showing that main shock was vertical in these areas. The locations of severe damage were situated along the Morimoto Fault, trending NE-SW in the north to central part of the city. Especially, the damage was serious on the southwestern end of the fault. The earthquake is believed to be caused by the Morimoto Fault with the epicenter located at the southwestern end of the fault.抄録全体を表示PDF形式でダウンロード (1382K) -
田中 愛一郎1986 年 39 巻 4 号 p. 665-666
発行日: 1986/12/25
公開日: 2010/03/11
ジャーナル フリーPDF形式でダウンロード (193K)
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