著者

早川 由紀夫 荒牧 重雄 高田 亮 浅岡 伸之 金子 隆之 津久井 雅志 岸 智 山下 茂 野原 状 平田 由紀子 小山 真人 白尾 元理 川辺 禎久

出版者

特定非営利活動法人 日本火山学会

雑誌

火山.第2集 (ISSN:24330590)

巻号頁・発行日

vol.32, no.3, pp.259-262, 1987-10-15 (Released:2018-01-15)

著者

津久井 雅志

出版者

特定非営利活動法人 日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.56, no.2-3, pp.65-87, 2011-06-30 (Released:2017-03-20)

参考文献数

27

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The 1783 activity of Asama volcano was reviewed from May to the end of the year based on 166 old documents, including those recorded at a distance. 1. Prior to the 1783 Asama eruption, the level of magma head ascended at Kama-yama crater-pit. Moderately explosive eruptions commenced on May 9, and repeatedly blew off the plugged magma. 2. Depending on the wind direction, ash fell N, NNE, and NE of the crater including Sado Island, Tohoku and Kanto districts. From August 3 to 5, climactic plinian eruption dispersed pyroclastic materials. Distributions of 8 tephra- fall units were presented. 3. The timing of rumbling and quakes at distant places farther than 100km from the crater well correspond with explosive events witnessed by neighbors of the volcano. 4. Duration of a single eruptive event rarely exceed 6 hours. It was true even during the culminating plinian stage from Aug. 3 to 5, 1783. The eruption was so violent in this stage that huge blocks larger than 10m were thrown from Kama-yama crater. 5. Documents concerning with Kambara pyroclastic flow and subsequent debris avalanche occurred on August 5, suggested that an explosion on the northern flank triggered collapse of northern sector. The event occurred at about 08:00 to 08:30am, which is 90 to 120 minutes earlier than estimations appear in previous work. 6. Small and less frequent eruptions continued until January 15, 1784.

著者

津久井 雅志

出版者

日本地球惑星科学連合

雑誌

日本地球惑星科学連合2016年大会

巻号頁・発行日

2016-03-10

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9世紀の巨大地震と火山活動の概要歴史時代の文献記録をまとめると,9世紀,15世紀末~16世紀,17世紀半,18世紀後半の噴火集中,19世紀半ばの地震・噴火などに「活動の集中期」があるように見える.ただし,発現のしかたは一様ではなく,時代ごとに違いが見られる.発表者は,9世紀の東日本~中部日本の地震・噴火活動を,2011年東北地方太平洋沖地震前に,地質,考古,文献に基づき以下のようにまとめた(津久井ほか,2007(地球惑星関連合同大会);津久井ほか,2008(火山)).1)富士山(800AD延暦噴火,838~864AD頃,864AD貞観噴火)・伊豆弧(伊豆大島(838ADころ~886ADにN3,N2,N1の3 噴火),新島(857ADころ,886ADの2噴火),神津島(838AD),三宅島,832AD?,850ADころ山頂噴火→山腹割れ目噴火の2噴火)の火山活動が極めて活発であり,鳥海山(810~823AD,871AD),新潟焼山(887AD?)でも噴火があった.2)日本海東縁沿い(秋田平野(830AD),庄内平野(850AD),越後平野(863AD)),糸魚川‐静岡構造線活断層系中~北部(841ADないし762AD),長野盆地西縁(887AD)?,関東内陸(818AD),北伊豆(841AD),伊勢原(878AD),南海トラフ(887AD)および東北沖(869AD,貞観地震)などで規模の大きな地震活動があった.3) 20世紀後半以降,9世紀の地変と重なる地域で地震・噴火が起きている,アムールプレートの東進が駆動力か?地震・噴火集中の直接的な原因は明らかではないが,連動したと考えられる噴火・地震はアムールプレートの境界に沿って800kmに及ぶ.大局的にはアムールプレートの東進(東日本に対して2cm/yr)による東西圧縮(石橋,1995,地質ニュース)に起因していると理解できる.日本海東縁ではアムールプレートは東日本(オホーツクプレートないし北米プレート)に対して沈み込み,糸魚川‐静岡構造線活断層系北部では東日本がアムールプレートに対し衝上する.一方,南海トラフではアムールプレートはフィリピン海プレートに沈み込まれる.その間にある糸魚川一静岡構造線活断層系中部は,左横ずれ成分を持ちながらアムールプレートを断ち切って沈み込み方向転換をする役割を担っている.9世紀の地震のうち起震断層を推定できたものは,東西圧縮と調和的な逆断層成分,横ずれ成分を持っている.このような条件下で固有の再来間隔が百数十年(南海トラフ)から千年以上(内陸地震)であるそれぞれの起震活断層が,短い期間に相次いで変位したのであろう.地震と火山活動の関連についての視点からみると,巨大地震のあとに火山活動が活発になった例は,869AD貞観東北沖地震のあとの871AD(貞観十三年)鳥海山噴火や,887AD仁和南海トラフ地震・長野盆地西縁断層地震直後?の新潟焼山噴火が挙げられ,これに915AD十和田を含めることができるかもしれないが,必ずしも巨大地震の後に一斉に火山活動が活発になるわけではない.伊豆諸島の噴火や864AD富士山貞観噴火は貞観東北沖地震や仁和南海トラフ地震に先立って噴火しているように見えるので,9世紀の場合は,巨大地震で圧縮応力が開放されてマグマの上昇が容易になる,というモデルで統一的に説明することは難しい.20世紀後半以降の地震・噴火20世紀後半には伊豆諸島(三宅島(1962AD,1983AD,2000AD(大規模貫入と2500年ぶり山頂カルデラ形成)),伊豆大島(1986AD(560年ぶり山腹割れ目噴火)),伊東沖噴火(1989AD(有史初めて))の噴火,日本海東縁沿い(新潟(1964AD,M7.5),日本海中部(1983AD,M7.7),北海道南西沖(1993AD,M7.8),新潟県中越(2004AD,M6.8),能登半島 (2007AD,M6.9),新潟県中越沖(2007AD,M6.8))で地震があり,9世紀との類似性を指摘していた(津久井ほか2007,2008前出)ところ,2011年3月11日に9世紀の貞観地震とよく似た東北地方太平洋沖地震(M9.0),翌日に長野盆地西縁断層北東延長で長野県北部地震(M6.7),2014ADに糸魚川‐静岡構造線活断層系北部で長野県神城断層地震(M6.7)が発生した.改めて9世紀の地変との類似性を意識して検討すべきである,と考えるに至った.しかし,9世紀の伊豆諸島の噴火ではマグマの頭位が高かったのに対し,20世紀後半以降マグマの貫入現象が目立ち三宅島では陥没カルデラが形成されるなど,噴火時の応力状態は異なっていたと考えられる.また,地震・噴火の発生の順序に規則性を見つけることも難しい.現時点でそれぞれの火山,震源断層の再来期間を考えると,平均的な再来期間を過ぎている糸魚川-静岡活断層系(と富士川河口断層帯),間もなく平均再来期間に達する南海トラフ,富士山噴火について注意深く監視を続けるべきだと考えている.

著者

津久井 雅志

出版者

特定非営利活動法人 日本火山学会

雑誌

日本火山学会講演予稿集 2017 (ISSN:24335320)

巻号頁・発行日

pp.68, 2017 (Released:2018-02-01)

著者

津久井 雅志

出版者

特定非営利活動法人日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.56, no.2, pp.89-94, 2011-06-30

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Old historical documents on 1779 AD An'ei eruption of Sakurajima, southwest Japan were collected from distal places as well as those from neighboring area of the volcano. These records revealed that the ash-fall front traveled to the northeast at about 50-100km/h, reached as far as Tohoku district 1200km from Sakurajima, and covered area of ca. 2.33×10^5km^2. Investigation of old documents helped to improve understanding of behavior of the volcano and environmental effects at the time of infrequent and great eruption. The wide distribution of ash-fall in 1779 Sakurajima eruption suggests that there is a high potential that ash discharged by future eruption of Sakurajima may cover down through the mainland of Japan. We should keep in mind both physical and economical effects of ash-fall in assessing the activity and making the scenario of an eruption.

著者

早川 由紀夫 荒牧 重雄 白尾 元理 小林 哲夫 徳田 安伸 津久井 雅志 加藤 隆 高田 亮 小屋口 剛博 小山 真人 藤井 敏嗣 大島 治 曽屋 龍典 宇都 浩三

出版者

特定非営利活動法人日本火山学会

雑誌

火山. 第2集 (ISSN:04534360)

巻号頁・発行日

vol.29, pp.S208-S220, 1984-12-28

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Stratigraphy and thickness distribution of the pyroclastic fall deposits formed during the eruption of Miyakejima volcano on October 3-4, 1983, were studied immediately after the deposition. Of the total mass of 20 million tons erupted, 8.5 million tons were ejected as basaltic scoria to form a complex set of air-fall deposits east of the fissure vents. One million tons of the latter were ejected from the upper fissures as fire-fountain products. The rest was the product of phreatomagmatic explosions which occurred in the lower fissures where ground water chilled the magma to form dense scoria blocks which devastated villages. Explosion craters and a tuff ring were formed along the N-S trending lower fissures. Account of the general distribution of the deposits, nature of the constituents, mutual stratigraphic correlation and correlation with observed sequence are given.

著者

小林 幹 津久井 雅志

出版者

特定非営利活動法人 日本火山学会

雑誌

日本火山学会講演予稿集 2016 (ISSN:24335320)

巻号頁・発行日

pp.151, 2016 (Released:2017-02-07)

著者

津久井 雅志

出版者

特定非営利活動法人 日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.56, no.2-3, pp.89-94, 2011-06-30 (Released:2017-03-20)

参考文献数

9

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Old historical documents on 1779 AD An’ei eruption of Sakurajima, southwest Japan were collected from distal places as well as those from neighboring area of the volcano. These records revealed that the ash-fall front traveled to the northeast at about 50-100km/h, reached as far as Tohoku district 1200km from Sakurajima, and covered area of ca. 2.33×105km2. Investigation of old documents helped to improve understanding of behavior of the volcano and environmental effects at the time of infrequent and great eruption. The wide distribution of ash-fall in 1779 Sakurajima eruption suggests that there is a high potential that ash discharged by future eruption of Sakurajima may cover down through the mainland of Japan. We should keep in mind both physical and economical effects of ash-fall in assessing the activity and making the scenario of an eruption.

著者

津久井 雅志

出版者

特定非営利活動法人 日本火山学会

雑誌

日本火山学会講演予稿集 2015 (ISSN:24335320)

巻号頁・発行日

pp.15, 2015-09-28 (Released:2017-02-10)

著者

津久井 雅志 荒牧 重雄

出版者

特定非営利活動法人日本火山学会

雑誌

火山. 第2集 (ISSN:04534360)

巻号頁・発行日

vol.35, no.2, pp.231-248, 1990-07-02

被引用文献数

5

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22,000 years ago, about 100 km^3 of magma erupted from the northrn end of Kagoshima Bay, southern Kyushu. The eruption produced 5 units of pyroclastic deposits; (1) 98 km^3 of airfall pumice (Osumi pumicde fall, OS), (2) 13 km^3 of oxidized, fine-grained Tsumaya pyroclastic flow (TSU), (3) Kamewarizaka breccia (KM) of the new vent-opening and enlargement stage, (4) 250 km^3 of Ito pyroclastic flow (ITO) at the climactic stage, (5) >50 km^3 of co-ignimbrite ash fall (AT ash). Phenocryst mineral assemblage throughout the whole sequence is ubiquitously plag+qtz+opx(Mg#45-60) +mt+il. One exceptional sample (ITO 11c) carries Fe-rich oliv (Fo 26-28) and cpx beside other phases. Fifty-five new XRF analyses of 10 major and 15 trace elements show that the majority of the erupted magma consisted of a remarkably homogeneous, high-silica rhyolite with SiO_2 74-76.5%(H_2O free and 100% normalized). The maximum fluctuation found both in major and trace elements is ±40%. These variations can be explained by the crystal-liquid separation near the roof of the magma reservoir. Mt-il temperatures and opx-mt-qtz pressures show narrow ranges, i e., 770±20℃ and 3-5 kb, respectively. Although the sample ITO 11c shows similar temperature, its calculated pressure is close to 0 kb. The bulk and mineral chemistry and the temperature-pressure estimation suggest that the magma reservoir was not distinctly zoned but was very homogeneous throughout prior to eruption.

著者

津久井 雅志 西戸 裕嗣 長尾 敬介

出版者

日本地質学会

雑誌

地質學雜誌 (ISSN:00167630)

巻号頁・発行日

vol.91, no.4, pp.279-288, 1985-04-15

被引用文献数

10 21

著者

津久井 雅志 中野 俊 齋藤 公一滝

出版者

特定非営利活動法人日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.53, no.2, pp.79-91, 2008-04-30

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Based on geological and archaeological data as well as historic documents, we review eruptions and earthquakes which have occurred during the 9th century in central and east Japan. The results reconfirm vigorous activities on Izu Arc, Izu-Oshima(〜838AD < N_3, N_2, N_1 < 886AD), Niijima(〜857AD and 886AD), Kozushima(838AD), Miyakejima(832AD and 850AD), and at Fuji volcano(800AD, 838AD < < 864AD, 864AD) during the 9th century. Beside these events, a big eruption of Niigata Yakeyama volcano had likely occurred in 887AD. Chokai volcano also erupted in 871AD, and 810-823AD. Collapse of Yatsugatake volcano took place in 887, probably invoked by a strong shock in 887. In addition, earthquakes with a magnitude from 7 to 8 had taken place along the Itoigawa-Shizuoka active fault system (in 841 or 762AD), Nagano fault system(887AD), Echigo plains(863AD), Shonai plains(850AD), Akita plains(830AD) and Nankai trough(887AD). As a result, we can point out a linkage of big eruptions and seismic activities in the 9th century over 800km long crossing Japan Arc. Geologically this seems to be a surface expression of East-West compression along eastern margin of Amurian Plate over 800km which was driven by the eastward motion of the plate. It is noteworthy to mention that the very similar volcanic and seismic activities have been occurring in the last 50 years to those happened in the ninth century, in their source areas and manners.