著者

秋 教昇 都司 嘉宣 朴 昌業 姜 泰燮

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.86, no.1-2, pp.11-27, 2011

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Recently, it was reported that Mt. Beakdu experienced at least four or five large volcanic eruptions in geological and historical times, and that the lake Cheonji had been formed by the collapse of a part of the mountain's summit (Wei et al., 1998). The last of four eruptions occurred in historical times. Geologists attempted to estimate the period of the eruptions using radio carbon isotope dating, but the results showed a variety of periods ranging from approximately AD 8th to 14th centuries, which are the dates of the Balae and Goryo dynasties. Unfortunately, there are no distinct records of eruptions during this period. In the present study, we suggest that the last great volcanic eruption occurred in winter when there was a strong northwestern seasonal wind, based on the distribution of pumice on satellite images and the thickness of pumice layers measured at sites in relationship to the climatic environment. On the other hand, some researchers interpreted that five events described in the Joseon Dynasty relate to volcanic eruptions of Mt. Baekdu. Those events occurred in 1413, 1593, 1668, 1702, and 1903. Their interpretations are widely cited in journals and books; however, based on critical reviews of historical literature including Joseon-wangjo-sillog ("Chronology of the Joseon Dynasty"), we found that three of the events were not related to volcanic eruptions of Mt. Beakdu. Events in 1413 and 1668 were Asian yellow sand storm. The event in 1903 recorded in Chinese literature (Liu, 1909) was found to be a shower of rain and hail accompanied by thunder and lightning. Only the two events in 1597 and 1702 were confirmed to be related to volcanic activities of Mt. Beakdu. According to Joseon-wangjo-sillog, a large earthquake with the maximum intensity of 9.0 on the Modified Mercalli Intensity scale (MMI) and its aftershocks occurred at the boulder region of Samsu county, Hamgyeongdo Province, in 1597. The document reveals that they were detected in Hamgyeondo (MMI6) and in Chungcheong-do (MMI5) over three days. The mainshock was accompanied by a volcanic explosion at Wangtian, which is located 35km southwest from Mt. Baekdu. The site is one of the three eruption centers of the Mt.Beakdu volcanic body. A document from China reveals that a large earthquake with an estimated magnitude of 7.0 and aftershocks occurred in the Gulf of Bohai on the same day as the Samsu earthquakes in Hamgyeongdo province. The shakes and disturbances observed eight times in Hamgyeong-do province might not be directly related to the large earthquake in the Gulf of Bohai. However, two series of earthquakes reported at two locations on the same day imply that there may be close relationships between the genesis of the two events. Based on phenomena observed recently, such as increased frequency of earthquakes, upheaval of ground level, releases of volcanic gases, and increased temperature of hot springs near the summit of Mt. Beakdu, the possibility of eruptions or explosions at the mountain in the near future has been suggested. Recently, scientists from the United States of America, Japan, Canada, and Germany were invited to investigate activity of the mountain. They agreed that the mountain is a dormant volcano and presents a temporal hazard.

著者

Kanamori Hiroo Miyamura Setumi

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.48, no.2, pp.115-125, 1970-06-10

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Old seismological data were used to re-evaluate the Great Kanto Earthquake of September 1, 1923. On the basis of reported P times at about one hundred stations the hypocenter parameters were determined as: origin time, 2h58m32s; latitude 35.4°N; longitude, 139.2°E; depth, 0 to 10km. The above epicenter may be uncertain by ±15 km. The surface-wave magnitude was re-evaluated using seismograms from 17 stations. The average value of 8.16 was obtained.|1923年9月1日の関東大地震の震源とマグニチュードを再決定した.震源決定に用いた資料はInternational Seismological Summaryや日本の文献に発表されているP波の発震時で約100の観測点の値を用いた.再決定された震源要素は次の通りである.震源時:02時58分32秒,震央緯度:35.4°N,震央経度:139.2°E,深さ:O~10km.この震央の誤差は±15km位である.マグニチュードの決定は,17ケ所の観測所で記録された周期20秒程度の表面波の振幅を用いて行なつた.平均値として8.16が得られた.

著者

羽鳥 徳太郎

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.51, no.2, pp.63-81, 1976-12-10

著者

2003年九州日奈久断層域構造探査グループ

出版者

東京大学地震研究所

雑誌

地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.83, no.1, pp.103-130, 2008

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The Hinagu fault system, Kyushu, Japan, is located in the westernmost part of the Beppu-Shimabara graben. This fault system is characterized by a quite high seismic activity and estimated to have a higher seismic risk among active faults in Kyushu Island. In 2003, we conducted an extensive seismic expedition in and around the Hinagu fault area. This expedition involves seismic refraction/wide-angle reflection experiment using dynamite shots and seismic array observation both for the active and passive seismic sources. For the refraction/wide-angle reflection study, two profile lines of 56.4 and 32.1km lengths were set in EW and NNE-SSW directions, respectively, on which 7 dynamite shots of 100-200kg charge and 359 recorders were deployed. The array observations, which were designed for high-resolution imaging of crustal scatterors and reflectors, were undertaken at 5 sites in the fault region. This paper presents the outline of this seismic expedition and fundamental data obtained.

著者

Kanamori Hiroo

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.49, no.1/3, pp.13-18, 1971-09-30

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The fault parameters of the Great Kanto earthquake of September 1, 1923, are determined on the basis of the first-motion data, aftershock area, and the amplitude of surface waves at teleseismic stations. It is found that the faulting of this earthquake is a reverse right-lateral fault on a plane which dips 34° towards N20°E. The auxiliary plane has a dip of 80° towards S55°E. This means that the foot-wall side moves approximately north-west with respect to the hanging wall side. The strike of the fault plane is almost parallel to that of the Sagami trough, and the slip direction is more or less perpendicular to the trend of the Japan trench. This earthquake is therefore considered to represent a slippage between two crustal blocks bounded by the Sagami trough. A seismic moment of 7.6×1027 dyne-cm is obtained. If the fault dimension is taken to be 130×70 km2, the average slip on the fault plane and the stress drop are estimated to be 2.1m and 18 bars respectively. This slip is about 1/3 of that estimated from geodetic data. This discrepancy may indicate an existence of a pre-seismic deformation which did not contribute to the seismic wave radiation, but the evidence from other observations is not very firm.|関東地震の断層パラメターをP波の初動分布と長周期表面波の振幅からきめた.その結果,この地震はN20°Eの方向に34°傾いた面上での右ずれ・逆断層であらわされることがわかつた.断層面の大きさを130×70km2とすると,断層面上でのすべりは約2m, stress dropは18バールである.断層上でのすべりのむきが相模troughの走向に平行で,日本海溝に垂直であり,また震源が浅く(地殻内)かつ日本海溝から遠くはなれていることを考ると,関東地震は海と陸のリゾスフィアの相互作用の直接の結果とは考えにくい.むしろ,この地震は海と陸のリゾスフィアの相互作用によつて2次的に起つた,相模troughを境とする二つの地塊のずれによるものであると解釈できる.地殻変動の大きさから推定されているすべりの大きさは7mであるが,これは表面波の振幅から推定された値2mよりはるかに大きい.この違いは種々の誤差を考慮にいれてもなお有意義と思われる.このくいちがいは,全体の地殻変動量のうち2分以内の時定数をもつもののみが地震波の発生に関与したと考えれば説明できる.

著者

高野 宏康

出版者

東京大学地震研究所

雑誌

歴史地震 (ISSN:13499890)

巻号頁・発行日

no.28, pp.91-107, 2013

著者

チリ津波合同調査班 編

出版者

東京大学地震研究所

巻号頁・発行日

1961

著者

金森 博雄

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.49, no.1, pp.13-18, 1971-09

被引用文献数

3

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The fault parameters of the Great Kanto earthquake of September 1, 1923, are determined on the basis of the first-motion data, aftershock area, and the amplitude of surface waves at teleseismic stations. It is found that the faulting of this earthquake is a reverse right-lateral fault on a plane which dips 34° towards N20°E. The auxiliary plane has a dip of 80° towards S55°E. This means that the foot-wall side moves approximately north-west with respect to the hanging wall side. The strike of the fault plane is almost parallel to that of the Sagami trough, and the slip direction is more or less perpendicular to the trend of the Japan trench. This earthquake is therefore considered to represent a slippage between two crustal blocks bounded by the Sagami trough. A seismic moment of 7.6×1027 dyne-cm is obtained. If the fault dimension is taken to be 130×70 km2, the average slip on the fault plane and the stress drop are estimated to be 2.1m and 18 bars respectively. This slip is about 1/3 of that estimated from geodetic data. This discrepancy may indicate an existence of a pre-seismic deformation which did not contribute to the seismic wave radiation, but the evidence from other observations is not very firm.|関東地震の断層パラメターをP波の初動分布と長周期表面波の振幅からきめた.その結果,この地震はN20°Eの方向に34°傾いた面上での右ずれ・逆断層であらわされることがわかつた.断層面の大きさを130×70km2とすると,断層面上でのすべりは約2m, stress dropは18バールである.断層上でのすべりのむきが相模troughの走向に平行で,日本海溝に垂直であり,また震源が浅く(地殻内)かつ日本海溝から遠くはなれていることを考ると,関東地震は海と陸のリゾスフィアの相互作用の直接の結果とは考えにくい.むしろ,この地震は海と陸のリゾスフィアの相互作用によつて2次的に起つた,相模troughを境とする二つの地塊のずれによるものであると解釈できる.地殻変動の大きさから推定されているすべりの大きさは7mであるが,これは表面波の振幅から推定された値2mよりはるかに大きい.この違いは種々の誤差を考慮にいれてもなお有意義と思われる.このくいちがいは,全体の地殻変動量のうち2分以内の時定数をもつもののみが地震波の発生に関与したと考えれば説明できる.

著者

羽鳥 徳太郎

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.62, no.2, pp.133-147, 1987-10-23

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日本海側に発生した元禄7年(1694)能代地震・宝永元年(1704)岩館地震・寛政4年(1793)鯵ケ沢地震および文化7年(1810)男鹿地震について,新史料を加えた震度分布図を示し,地震の規模を検討した.一方,史料をもとに各地の津波の高さを現地調査し,津波の規模を考察した.1939年男鹿地震(M=7.0)の震度分布と比べると,鯵ケ沢地震の規模はM=7.2,能代地震・岩館地震・男鹿地震はいずれもM=7.0と推定される.これらのマグニチュード値は,従来のものより0.1~0.2大きい.鯵ケ沢地震では鯵ケ沢~深浦間で3~5mの波高が確められ,津波マグニチュードはm=1と推定される.岩館地震の潮位記録は,深浦~滝ノ間間で0.6~1.4mの津波が伴ったことを示唆しており,津波マグニチュードはm=Oとみなせる.また,能代地震・男鹿地震では20~30cmの津波があったと考えられる.震度・津波および地殻変動のデータを考え合せると,震源域は西津軽~男鹿沿岸にそって並び,震源の大きさは30~50kmと推定される.

著者

羽鳥 徳太郎

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.53, no.2, pp.423-445, 1978-09-30

著者

羽鳥 徳太郎

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.55, no.2, pp.505-535, 1980-11-15

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There are many old monuments of the Nankaido tsunamis of Hoei (Oct. 28, 1707) and the 2nd Ansei (Dec. 24, 1854) along the Osaka and Wakayama coasts, Western Japan. Most of these monuments were built just after the earthquakes to pray for the repose of the tsunami victims or to sound a warning to inhabitants. In this paper, the tsunami monuments are illustrated. Based on descriptions on the monuments, adding new data collected from the present field investigation, inundation heights of the 1707 Hoei and 1854 Ansei tsunamis along the Wakayama coast are surveyed by hand-level. Behaviors (inundation height and area) of the two historical tsunamis are compared with those of the 1946 Nankaido tsunami (Dec. 21, 1946). Inundation heights of the 1854 Ansei tsunami along the Wakayama coast, the west side of the Kii Peninsula, are 4.8 meters on the average and are 1.2 times as large as those of the 1946 Nankaido tsunami. The estimated heights of the 1707 Hoei tsunami are 5 meters with the localized run-up maximum of 6 to 7 meters. Along the Wakayama coast, the patterns of height distribution of the two historical tsunamis are similar to that of the 1946 Nankaido tsunami. However, the inundation heights of the 1707 Hoei and 1854 Ansei tsunamis along the coast in Osaka Bay are three times as large as those of the 1946 tsunami. Osaka suffered severe damage and many persons were drowned by the two tsunamis of 1707 and 1854. Estimated heights were about 3 meters. It suggests that the wave periods of the two historical tsunamis were longer than those of the 1946 tsunami. Although the source dimensions of the two historical tsunamis are similar to the 1946 tsunami (The source areas of three tsunamis extend 250 km along the Nankai trough), the rise times of crustal deformation for the two historical earthquakes differ significantly from the 1946 earthquake.

著者

羽鳥 徳太郎

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.61, no.1, pp.143-157, 1986-08-04

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秋田県南部の象潟・金浦海岸に顕著な地殻変動と地震・津波被害をもたらした文化元年(1804年)象潟地震について,新史料を加えて震度分布を調べ,地震の規模を検討した.一方,津波史料をもとに各地の津波の高さを現地調査し,津波の規模および発生機構を考察した.震度6の範囲が本荘~酒田間60kmに及んだことは,今村の報告(1921)と変わりはないが,震度4の地域は青森・宮城県および新潟県下にまたがつた.その広がりから地震のマグニチュードはM=7.3と推定される.海岸の地盤高をふまえて津波の被害状況をみると,津波の高さは象潟付近で平均海面上4~5m,酒田では3~4mと推定される.そのほか周辺の波高分布から判断すれば,津波マグニチュード(今村・飯田スケール)はm=1.5と格付けできる.震度・地殻変動の分布を考え合せると,波源域の長径は本荘~酒田沿岸南北方向に,60kmと推定される.津波の規模は地震の規模に対して標準以上に大きく,この津波は高角の逆断層で起こされたものと考えられる.

著者

葉室 和親 荒牧 重雄 藤岡 換太郎 石井 輝秋 田中 武男 宇都 浩三

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.58, no.2, pp.527-557, 1983-10-22

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1979年12月の淡青丸KT-79-18航海の際,東伊豆沖海底火山群,大島南方の大室出シ堆,新島東方の新島ウラノ瀬などの海底火山の岩石をドレッジにより採集した.東伊豆沖海底火山群は,岩石の鉱物・化学的特徴により北半部,中部,南部に細分することができる.北半部の岩石はすべて高アルカリソレアイト系列の玄武岩・安山岩溶岩であり,伊豆半島中部東部に分布する東伊豆単成火山群がそのまま海底に延長して孤立した海底火山として分布しているものと考えて差支えない.中部では,低アルカリ(低Na2O)ソレアイト系列の玄武岩が5点のドレッジから発見された.そのうち伊豆大島に近い2点は,伊豆大島火山の玄武岩類に似た鉱物・化学組成をもち,新鮮である.西側の3点の岩石はいずれも風化変質作用を受けており,小角礫の集合として産する.これらは伊豆大島火山や東伊豆単成火山群よりも古い海底火山に属するものと判断される.南部のドレッジ2点からは東伊豆単成火山群南西部のグループの岩石に似た玄武岩が得られた。大室出シは,ガラス質多孔質の新鮮な流紋岩溶岩流から成る平坦な頂部をもつ海底火山と考えられる.山体の中央部に深さ100m,長さ1.5km,幅0.5kmの凹陥地(大室海穴)があるが,その壁からは流紋岩溶岩が採集された.新島ウラノ瀬の南東麓からは,流紋岩溶岩と変質した玄武岩礫,石英閃緑岩礫などが採集された.後者はこの地域を構成する基盤岩類と考えられる.

著者

島 悦三 柴野 睦郎

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.34, no.1, pp.113-129, 1956-06-25

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People in the Futatsui area in Akita Prefecture experienced a severe earthquake at 1h 45 m 33s (G. M. T.) on Oct. 19th, 1955 for the first time in local history. Fortunately to say, the earthquake was only semi-destructive in its intensity, the stricken area being confined to the Futatsui town and the Hibiki village which suffered no less of life and only 4 casualties. Owing perhaps to the structural quality of the houses in the district, only 3 wooden houses were half destroyed. But curiously, the "dozo's" or warehouses sustained severer damage, 310 of them being reported as half-destroyed, while one was totally destroyed.

著者

中村 一明 笠原 慶一 松田 時彦

出版者

東京大学地震研究所

雑誌

地震研究所研究速報

巻号頁・発行日

vol.8, pp.73-90, 1964-09

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昭和39年6月16日新潟地震調査概報

著者

Ando Masataka

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.49, no.1-3, pp.19-32, 1971-09-30

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The writer determined fault parameters of the great Kanto earthquake of 1923 on the basis of the geodetic data by triangulation and levelling. Thus he attempted to establish a dislocation model which reasonably explains all the available data on the surface displacements associated with this earthquake. Basically the fault line is assumed to extend from the Kozu area southeastward with its strike N45°W, parallel to the trend of the Sagami trough. The shape of the fault plane is assumed to be a rectangular plane. The fault models which was finally accepted is as follows. total length: 130km, width: 65km, dip. 45° and a fault displacement : 6 m (right lateral strike slip) and 3 m (reverse dip slip). Generally speaking, this earthquake seems to indicate a differential movements of the two crustal plates bounded by the Sagami trough. The fault's dimension, geometry and direction of the slip are all in good harmony with the seismological evidence on wave radiation.|1923年の関東大地震の震源パラノーターを地殻変動を使つて推定した.

著者

羽鳥 徳太郎

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.51, no.2, pp.63-81, 1976-12-10

著者

木村 敏雄

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.44, no.2, pp.561-607, 1966-10

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Turbidites are developed in the Permian-Triassic Sambosan and the Jurassic-Cretaceous Shimanto group in Japan. The Turbidite sequences are well distributed in the Tamagawa district, the Kanto mountainous land, and in the Oigawa district (Fig. 1). The sequence in the latter district occupies the southern wing of a grand recumbent fold. Here, turbidite-poor shale, turbidite (the A formation), non-turbidite with turbidite (the B), turbidite (the C) and turbidite-poor shale formations are distributed. Average thickness and standard deviation of the sandstone and shale beds within each 5m column of strata were measured (Tables 1-3). Average thickness of sandstone beds varies with the horizon, especially with the major cyclic sedimentation. On the other hand the average thickness of shale beds is fairly constant in the turbidite sequences (the A and C formations). Thickness of the sandstone beds in the turbidite sequences shows log-normal distributions (Figs. 16, 17). However, that of the shale in the turbidite sequences shows distributions similar to the normal ones. The distributions are probably due to the fact that the shale deposition is proportional to time and that the time interval of turbidity currents is fair constant. This is confirmed by a fact that the number of turbidites during the deposition of a unit shale is fairly constant (Table 4). The standard deviation of thickness distribution is related to the thickest bed within each 5m column, especially for the sandstone beds. Thickness distributions of sandstone and shale beds in the turbidite-poor and the turbidite-rich sequences (the B formation) are quite different from those of the turbidite sequence (the A and the C formation) in the Oigawa (Fig. 18, Table 2) and show much wider distribution. The thickness of sandstone beds is not related to that of the overlying and the underlying shale beds in the A and C formation (Figs. 22, 23). However, turbidite beds in the turbidite-poor shale formation underlying the A formation are composed of a very thin sandstone part and rather thick silt part. In this case thickness of the overlying silt and shale appears to be related to that of the underlying sandstone part. The thickness of turbidite sandstone beds is also related to the clasticity (Fig. 24) and sedimentary structures. Sole marking is not common on the underside of the thinner beds (70cm or less). Laminated structures, convolute structures and other are common in the thinner beds (10cm or less), but not common in the thicker beds. In the turbidite together with the non-turbidite sequences there are cyclic sedimentations. Sandstone-shale diagrams (Figs. 6, 10, 11, 14, 15), total thickness (Figs. 4, 7, 13), average thickness and the thickest bed (Fig. 26) within 5m column, and accumulation of sandstone during the deposition of a unit thick shale (Figs. 8, 10, 15) show the cyclic sedimentations which are classified into major and minor ones. The major cyclic sedimentation is most well shown by the distribution of thickest bed within each 5m column (Fig. 26). The bed usually corresponds to the thickest bed within each minor cycle (Fig. 19). The major cycle may be related to transgression and regression and is not related to the chert deposition at Unazawa (Fig. 7). Minor cyclic sedimentations are further classified into "increasing" and "decreasing" types (Fig. 12). The "increasing" type appears to be generally formed during the regression, the "decreasing" type during the transgression. The minor cyclic sedimentations are well shown by the sandstone-shale diagrams as well as by the thickness distribution of sandstone beds according to the sedimentation order (Figs. 12, 20). There was a basin of the normal sedimentation with some steep cliffs at the regressional stage (Fig. 27), a part of this basin becoming the drainage of turbidity currents when the sea level was rather high. At the stage of transgression, shale deposited principally with muddy turbidites. The major cyclic sedimentation may have been formed under such a circumstance. The frequency of great earthquakes and the tectonic position in the westernmost Pacific near Japan are comparable with those of turbidite sequences in the Oigawa district, the turbidites having been probably produced by such earthquakes.二畳紀-三畳紀の三宝山層群,ジュラ紀-白亜紀の四万十層群にはTurbidites層が発達している.このTurbidite層は多摩川地域・南部大井川地域によく見られる(Fig. 1).大井川地域のこの層群は大きな横臥せしゅう曲の南翼をなしており, Turbiditeの少ない頁岩層, Turbidite層(A層), Turbiditeを伴うnon-Turbidite層(B層), Turbidite層(C層), Turbiditeの少ない頁岩層からなつている. 5mの厚さの地層の中の砂岩層の平均層厚(Table 1-3)は層準に応じて,特に堆積の大りんねに応じて変化する.一方頁岩層の平均屈厚はA, C層内では層準にかかわらずほぼ一定である.

著者

東京大学地震研究所 [編]

出版者

東京大学地震研究所

巻号頁・発行日

1977

著者

長沢 工

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.53, no.1, pp.p271-280, 1978