著者

大井田 徹 山田 功夫 多田 堯 伊藤 潔 杉山 公造 佐々木 嘉三

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.24, no.3, pp.240-247, 1971

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In order to study the seismic activity of microearthquakes in the southern part of the Neo Valley fault, an observation was carried out in 1968 from September 27 to November 2. Seven observing stations were set near the four stations of Inuyama Seismological Observatory.<br>About 400 microearthquakes were recorded during this observation, but about 50 epicenters could be determined. Their magnitudes were less than 2.<br>Microearthquakes occurred most frequently in the southwestern side of the fault, especially in the area upheaved by the Nobi earthquake of 1891. On the contrary, very few earthquakes occurred in the northeastern side. The focal depths of these shocks were very shallow.

著者

高野 和友 木股 文昭

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.62, no.2, pp.85-96, 2009

被引用文献数

1

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This study reexamines the ground deformation and fault slip model of the 1945 Mikawa earthquake (<I>M</I> =6.8), central Japan. We reevaluate two geodetic data sets from the years 1886/1887 and 1955/56 that were obtained from the Geographical Survey Institute; these data sets consist of displacements calculated from the net adjustment of triangulation surveys carried out before and after the Mikawa earthquake. We remove the interseismic deformation and coseismic deformation of the 1944 Tonankai earthquake from the two unique data sets used in our analysis. Maximum coseismic horizontal displacements of over 1.4 m were detected to the west of the Fukozu fault. We estimated the coseismic slip by analyzing our data set. The geometry of the fault planes was adopted from a recent seismicity study and from the surface earthquake fault of this area. The best fit to the data is obtained from two faults along the sections running north and south of the Fukozu and Yokosuka faults. The estimated uniform-slip elastic dislocation model consists of two adjacent planes. The fault also appeared to connect the sections running north and south of the Fukozu and Yokosuka faults. Because it can suitably explain the coseismic deformation due to two earthquake source faults, the earthquake source fault is not admitted under the section for the run. The mechanism is considered to be two reverse faults with right-lateral components. The estimated slips for the two source faults are 2.5 m and 1.4 m, respectively. The pressure axis is directed along NE-SW or E-W. The total seismic moment determined from this model is 1.6 &times; 10<SUP>19</SUP> Nm, corresponding to <I>M</I><SUB>w</SUB>=6.7.

著者

石橋 克彦

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.26, no.4, pp.362-367, 1973-12-30 (Released:2010-03-11)

参考文献数

11

著者

永田 武

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.8, no.9, pp.447-456, 1936

著者

加納 靖之

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.70, pp.171-182, 2017-11-10 (Released:2017-12-12)

参考文献数

64

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It has long been believed that a M6.1 earthquake occurred on November 14, 1831 in Saga, southwest Japan. The event relies on a single entry from note of “Tenpo Zakki,” which is a collection of miscellaneous notes between 1831 and 1844. Here we propose that the location for the earthquake is likely misinterpreted. Reexamination of the note shows that the earthquake occurred on November 13, 1831, as was recognized in 1919. The original location was thought to be in Saga because according to the note the earthquake was reported from “Hizen-no-kami” (lord of Saga). Analyses of the time it took for the news to reach Edo (Tokyo) show that the location of the earthquake is possibly not Saga, but Aizu, in northeast Japan. The note of “Tenpo Zakki” shows that the information of the event reached Edo in 5 days. However, it was impossible to deliver a letter from Saga to Edo in 5 days at that time. No description on the earthquake was found in diaries written around Saga. “Tenpo Zakki” might have mistaken “Higo-no-kami” (lord of Aizu) for “Hizen-no-kami.” This result contributes to improvement of the list of historical earthquakes for Japan.

著者

南雲 昭三郎

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.22, no.3, pp.247-248, 1969-11-30 (Released:2010-03-11)

参考文献数

4

著者

八木 勇治 菊地 正幸 吉田 真吾 山中 佳子

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.51, no.1, pp.139-148, 1998-07-03 (Released:2010-03-11)

参考文献数

26

被引用文献数

16 23

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We investigate the rupture process of Hyuga-nada earthquake of April 1, 1968 (MJMA 7.5). Applying a multiple-time window inversion scheme to teleseismic body wave data, we obtained a detailed spatio-temporal distribution of moment release. The main source parameters are: the seismic moment=2.5×1020[Nm]; the rupture area=64×48[km2]; the stress drop=3.4[MPa]; the focal depth=15[km]. The rupture consists of three major asperities: the first asperity centring about 10km south and 20km west from the hypocenter and having a maximum slip of 4.0m, the second one centring about 8km north and 5km east from the hypocenter and having a maximum slip of 3.0m, and the third one centring about 50km west from the hypocenter and having a maximum slip of 3.2m. We compared the rupture area with that of a few large events (M>6.5) subsequent to the 1968 event. Then we found that the above three asperities of 1968 event coincide with the low seismicity area in the Hyuga-nada region, and do not overlap with the source area of the subsequent large events (M>6.5). This rupture pattern and the seismicity suggest that an area of slab bending as well as fracture of the slab can behave as barriers during earthquake rupture. These barriers may control the maximum size of earthquake source in this region.

著者

山田 祐子 廣田 伸之 新原 俊樹

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.74, pp.1-10, 2021

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<p>In a small area off the eastern coast of Osumi Peninsula, eight events have been observed from January 2001 to March 2019, in which <i>M</i>3 to <i>M</i>4 earthquakes occurred successively in a short time, from several seconds to several minutes. Based on the waveform correlation and cluster analysis, we found three seismic patches (asperities) which generate small repeating earthquakes in this area. The arrival time differences between P and S waves of the three patches' earthquakes observed at NARU station suggested that these patches were close to each other. Furthermore, we confirmed that many earthquakes originated from these patches were included in the successive occurrences of earthquakes in this area. These results suggest that the earthquake from one of these patches affects another patch in the immediate vicinity and triggers successive occurrences of earthquakes.</p>

著者

海野 徳仁 長谷川 昭

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.35, no.2, pp.237-257, 1982-06-25 (Released:2010-03-11)

参考文献数

13

被引用文献数

10 10

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A precise relocation of earthquakes using data listed in the Seismological Bulletin of the Japan Meteorological Agency reveals a double-planed structure of the deep seismic zone in the whole region of the northeastern Japan arc. The two planes are nearly parallel to each other and the distance between them is from 30km to 40km. The lower seismic plane appears at depths greater than about 60km in the Tohoku District, northeastern Japan, while that appears at depths greater than about 90km in the Kanto District.Some interesting characteristics are found from focal mechanism study for large earthquakes and microearthquakes in the upper seismic plane. In the Tohoku District, the predominant fault-plane solution for earthquakes shallower than about 60km is low angle thrust faulting and that for deeper earthquakes is down dip compression. In the Kanto District, similar characteristics are found for earthquakes in the upper seismic plane, except that the depth at which the predominant focal mechanism changes is about 90km. This difference may be closely associated with the subduction of the Philippine Sea plate overriding the Pacific plate in the Kanto District.In the whole region of the northeastern Japan arc, the earthquakes in the lower seismic plane is characterized by down dip extensional fault. Down dip compressional and down dip extensional earthquakes form a pair in the double-planed deep seismic zone, since the depth at which the lower seismic plane appears is consistent with the depth at which the predominant focal mechanism changes in the upper seismic plane.The depth to the upper seismic plane just beneath the volcanic front is about 100km in the Tohoku District, whereas the depth is much deeper in the Kanto District, where the triple junction among the Philippine Sea plate, the Pacific plate and the Eurasian plate is situated.

著者

飯塚 進

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.29, no.4, pp.365-374, 1976

被引用文献数

1

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There is a remarkable discrepancy in the previous results on the temporal variations in seismic wave velocities related with the Matsushiro earthquake swarm that have been studied by many investigators. A result from the <i>V_p</i>/<i>V_s</i> method shows co-seismic anomaly, while all the data from the P-residual method indicate precursory anomaly.<br>To make clear the cause of this discrepancy, temporal changes in <i>V_p</i>/<i>V_s</i> ratio was reexamined by using the different set of data source from previous studies. Two kinds of velocity anomalies, namely, precursory and co-seismic or post-seismic anomaly were detected as the same as in the previous investigations.<br>Combining the present data with the data from previous studies, it was inferred that the precursory anomaly in seismic velocities might occur mainly in the zone of lower crust to the uppermost mantle, while the co-seismic or post-seismic anomaly might occur in the upper part of crust whose depth is not greater than 10km, underneath at and adjacent area of the Matsushiro earthquake swarm. In other words, the anomalous zone must have migrated from the deeper parts to the upper crust about the time when the swarm began.<br>The origin of these two anomalies were interpreted by a new model which takes thermal effects into consideration for earthquake occurrences.

著者

長谷川 昭 堀内 茂木 植木 貞人 西澤 あずさ 松澤 暢 海野 徳仁 堀 修一郎 稲盛 隆穂 松本 聡 浜口 博之 高木 章雄 田中 和夫 鈴木 将之 末広 潔

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.42, no.2, pp.161-169, 1989-06-24 (Released:2010-03-11)

参考文献数

17

被引用文献数

1 1

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A seismic refraction experment was carried out around the Bandai volcanic area, the southern part of the Tohoku District, by using a large capacity (9 liter air chamber) marine airgun. Shallow crustal structure (down to about a 4km depth) obtained along the 30km-length profile shows the swelling of the second layer with P-wave velocity more than about 4.0km/s just beneath Bandai volcano in parallel to the surface topography. The swelling of the second layer by about 1km is in good agreement with that of the basement estimated from the Bouguer anomaly.Seismic signals from the surrounding telemetered stations of Tohoku University at epicentral distances from 10km to 230km, are continuously recorded during the airgun experiments. In the stacked records we can detect the clear first P arrivals from the airgun shots at the stations with distances ranging up to 150km, which shows the usefullness of the marine airgun for studying the crustal structure on land. Anomalously late P arrivals or unclear P arrivals are observed for the ray paths which cross active volcanoes. This result and the shallow crustal structure obtained along the refraction profile suggest the existence of the anomalous zone beneath Bandai volcano at depths deeper than about 4km.

著者

小林 昭夫 弘瀬 冬樹 堀川 晴央 平田 賢治 中西 一郎

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.70, pp.221-231, 2018

被引用文献数

2

著者

那須 信治

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.34, no.special, pp.123-134, 1981-09-25 (Released:2010-11-17)

被引用文献数

1

著者

小山 順二 都筑 基博

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.66, no.4, pp.83-95, 2014-03-25 (Released:2014-05-20)

参考文献数

59

被引用文献数

1 1

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After the 2011 Tohoku-oki megathrust earthquake of Mw 9.0, we observed tens of thousands of inland and volcanic earthquakes all over the Japan Islands, which are not confined within the aftershock area of off the Pacific coast of Tohoku region. This reminds us to evaluate the earthquake activity in a much wider sense, discarding an ordinary idea of the foreshock-mainshock-aftershock activity within a limited aftershock area of a particular earthquake. There occurred several megathrust earthquakes worldwide in the last one hundred years. We have studied their significant events before and after the earthquakes based on our new hypothesis on the earthquake generating zone with the distinct difference between Along-dip Double Segmentation (ADDS) and Along-strike Single Segmentation (ASSS). In summary, some of significant aftershocks (larger than Mw 7.5) of ADDS megathrusts are those (Type I) in and near outer-rises, where some are dip-slip normal faultings and some are strike-slip faultings within subducting oceanic plates with component of normal fault. These outer-rise earthquakes are considered to be controlled by the slab-pull of descending slabs of oceanic plates induced by the reduction of plate couplings by megathrusts. In addition, some are also significant (Type II) along the plate interfaces within aftershock areas and those extending aftershock areas similarly to the corresponding megathrusts. On the other hand, aftershocks of ASSS occurred in and near corresponding aftershock areas and significant and or disastrous outer-rise events are rare. Some large (not significant) inland earthquakes are also known for both ADDS and ASSS megathrusts. All these results are not dependent on whether the subduction geometry is oblique or orthogonal.

著者

竹内 均

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.27, no.3, pp.274, 1974-09-30 (Released:2010-03-11)

参考文献数

2

著者

表 俊一郎

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.15, no.5, pp.101-113, 1943

著者

飯尾 能久

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.39, no.4, pp.645-652, 1986-12-25 (Released:2010-03-11)

参考文献数

6

被引用文献数

2

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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.

著者

岩城 麻子 岩田 知孝 関口 春子 浅野 公之 吉見 雅行 鈴木 晴彦

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.61, no.4, pp.161-173, 2009

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We studied the source model and the underground velocity structure model for quantitative estimation of long-period (3-20s) ground motion in the Oita Plain due to a hypothetical Nankai earthquake. First, the deep subsurface velocity structure of the Oita sedimentary basin was validated by a long-period ground motion simulation of the 2000 western Tottori earthquake records. The simulated waveforms reproduced the amplification and duration of the observed waveforms and peak periods of pseudo response spectra at strong motion stations both in and out the Oita Plain reasonably well. Then we combined the subsurface velocity structure with a crustal velocity structure and performed long-period ground motion simulations of a Nankai earthquake by a three-dimensional finite-difference method. The source model has a total area of 34,000 km<SUP>2</SUP> with total seismic moment of 6.24&times;10<SUP>21</SUP> Nm (<I>M</I><SUB>W</SUB> 8.5). In addition to the scenario in which rupture propagates from the east (east-hypo model) that have been generally accepted, we investigated another from the west (west-hypo model). For the east-hypo model, the maximum amplitudes of the simulated horizontal ground motion in the Oita plain was three to four times as large as that on a rock site beside the plain. Especially in the bay area, the maximum ground motion reached 100cm/s and the pseudo velocity response spectra at period 6-8s were more than 400cm/s. On the other hand, the ground motion simulated by the west-hypo model was roughly one fifth smaller than that by the east-hypo model. It is also pointed out that in the east-hypo model simulation, the seismic waves generated by the two asperities near to the Oita plain are enlarged due to the directivity effect and amplified and prolonged by the sedimentary basin structure.

著者

松村 正三

出版者

公益社団法人 日本地震学会

雑誌

地震. 2輯 (ISSN:00371114)

巻号頁・発行日

vol.49, no.1, pp.85-88, 1996-05-24

参考文献数

15

被引用文献数

3

著者

齊田 時太郎

出版者

公益社団法人 日本地震学会

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.6, no.6, pp.318-325_1, 1934-06-15 (Released:2010-03-09)