著者

宮町 宏樹 泊 知里 八木原 寛 井口 正人 為栗 健 山本 圭吾 大倉 敬宏 安藤 隆志 尾西 恭亮 清水 洋 山下 裕亮 中道 治久 山脇 輝夫 及川 純 植木 貞人 筒井 智樹 森 済 西田 誠 平松 秀行 小枝 智幸 増田 与志郎 加藤 幸司 畠山 謙吾 小林 哲夫

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.58, no.1, pp.227-237, 2013-03-29

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2008年に実施された屈折法地震探査によって得られたP波初動走時により,姶良カルデラおよび桜島火山の深さ3kmまでの速度構造を推定した.本研究地域の基盤層である四万十層群は4.6-5.0km/sのP波速度を持ち,姶良カルデラの中央部に向け傾斜している.姶良カルデラの中央部には,4.2-4.4km/sの低速度域が深さ1.5-3kmに存在している.そして,この低速度域はカルデラ下に存在する深部マグマ溜まりからのマグマ供給系が活発であることを示唆している.また,基盤層は鹿児島地溝帯の北西域の境界に沿って深さ1kmから2.5kmに急激に落ち込んでいることがわかった.桜島火山の速度構造は3.6-3.7km/sの領域が存在することで特徴づけられる.桜島火山の山頂直下で発生している火山性地震の震源域と速度構造の比較から,地下構造が種々の火山性地震の震源域の広がりに強い影響を与えていることを示した.

著者

土屋 美穂 萬年 一剛 小林 淳 福岡 孝昭

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

巻号頁・発行日

vol.2012, 2012-10-14

著者

大場 武 片渕 雄次 中村 一茂 及川 光弘 大和田 道子 水橋 正英

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

巻号頁・発行日

vol.2002, no.2, 2002-10-22

被引用文献数

2

著者

原田 昌武 細野 耕司 小林 昭夫 行竹 洋平 吉田 明夫

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.55, no.4, pp.193-199, 2010-08-31

被引用文献数

1

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Temporal changes in dilatational strain and the activity of low-frequency earthquakes around Mt. Fuji and Hakone volcano are investigated. It is shown that both cumulative strain and cumulative number of low-frequency earthquakes around Mt. Fuji have been increasing since the end of 2006. The tendency is more notable for relatively larger earthquakes rather than smaller earthquakes. The b value for earthquakes during the period after November 2006 is significantly smaller than the b value during the period from January 2004 through October 2006. These facts suggest that the crustal stress surrounding the source region of low-frequancy earthquakes has been increasing. We think this is the cause of the dilatational strain observed around Mt. Fuji. On the other hand, a clear relationship is not seen between extensional strain events observed three times since 2001 and the activity in low-frequancy earthquakes around Hakone volcano.

著者

為栗 健 MARYANTO Sukir 井口 正人

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.52, no.5, pp.273-279, 2007-10-31

被引用文献数

2

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桜島火山において発生するハーモニック微動のモーメントテンソル解析を行った.B型地震群発後に発生する微動(HTB)と爆発的噴火直後に発生する微動(HTE)のモーメントテンソル成分に大きな違いはなく,等方成分は50%以上,CLVD成分は20〜30%,DC成分は20%以下であった.鉛直方向のダイポール成分が大きく,鉛直方向の力が優勢な震源が推定される.震源は火口直下の浅部であり,爆発的噴火発生前に火口底直下に形成されているガス溜まりが微動の発生に関与していると考えられる.

著者

水上 武 茂木 清夫 平賀 士郎 宮崎 務

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.2, no.2, pp.77-90, 1957-12-30

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Volcano Sakura-zima resumed explosive eruption in its summit crater after a long repose on Oct. 13. 1955, and is still active up to the present (Oct. 1957). In order to throw a light on the relation between explosive eruptions and volcanic earthquakes, we applied to this volcano the same method of seismometrical observation as being carried out in Volcano Asama. As the result, we observed four types of volcanic earthquakes originating from Sakura-zima: Namely, 1) volcanic earthquakes of the A type, 2) volcanic earthquakes of the B type, 3) earthquakes accompanied by explosive eruptions and 4) volcanic pulsation of continuous train (or harmonic tremor). On the basis of the seismometrical observation at four or six stations, we determined localities of these earthquakes of the four types. As the result, it was made clear that the epicentral area of the B type earthquakes, the explosion earthquakes and the volcanic pulsation agree with the locality of the active crater on the summit, and the A type earth quakes are originated from deeper part of the volcano. From the illustration of seismic activity and explosive eruption in Fig. 5, it seems that frequency of the B type earthquakes harmonizes with the eruptive activity. After precise examination of the development of the mentioned phenomena, we find that marked swarms of the B type earthquakes preceed in many cases to respective swarms of explosive eruption by ten or fifteen days. However, the problem is not always simple. It is neccessary to continue the observation not only in active state of the volcano but also in its calm state.

著者

吉田 明夫 瀬野 徹三

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.37, no.6, pp.297-301, 1992-12-25

被引用文献数

4

著者

上澤 真平

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.6, pp.171-191, 2008-12-29

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On May 24^<th> 1926, the eruption of Tokachidake volcano, in central Hokkaido, efficiently melted the snow pack on the hill slope, triggering the Taisho lahar which killed 144 people in the towns of Kamifurano and Biei. A geological survey and paleomagnetic and granumetric studies were conducted on the northwestern slope of Tokachidake volcano to reconstruct the sequence of the 1926 eruption and decipher the triggering mechanism for the Taisho lahar. The Taisho lahar deposits in the proximal area of the volcano are divided into five distinct units (unit L1, L2, and A through C, from oldest to youngest). Unit L1 is an older lahar deposit that underlies the 1926 deposits. The 1926 sequence consists of debris avalanche deposits (unit A and C), a laminated sandy debris flow deposit (unit B), and a lahar deposit including scoria clasts (unit L2). Each unit contains hydrothermally altered rocks and clay material with more than 5 wt.% fragments smaller than 2mm in diameter. The progressive thermal demagnetization experiments show that the natural remanent magnetization (NRM) of all samples in unit A, B and C have a stable single or multi-component magnetization. The emplacement temperatures are estimated to be normal temperatures to 620℃ for unit A, 300 to 450℃ for unit B, and normal temperature to 500℃ for unit C. On the basis of geological and paleomagnetic data and old documents, a sequence for the eruption and the mechanism of formation and emplacement of the Taisho lahar can be reconstructed. The first eruption at 12: 11 May 24th triggered a small lahar (unit L2). Collapse of central crater at 16:17 May 24th 1926 then resulted in a debris avalanche containing highly altered hydrothermal rocks with hot temperatures ranging from 300 to 620℃ (unit A). The debris avalanche flowed down the slope of the volcano, bulldozing and trapping snow. Immediately following the collapse, a hot (approximately 400℃) hydrothermal surge (unit B) melted snow and transformed into a lahar causing significant damage and deaths in the towns downstream. Just after the generation of the lahar, another collapse occurred at the crater causing another debris avalanche (unit C).

著者

井口 正人 中道 治久 為栗 健 山本 圭吾

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

巻号頁・発行日

vol.2014, 2014-11-02

著者

萬年 一剛 原田 昌武 板寺 一洋 代田 寧 寺田 暁彦

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

巻号頁・発行日

vol.2013, 2013-09-29

著者

古川 邦之 鎌田 浩毅

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

巻号頁・発行日

vol.2004, 2004-10-19

著者

池田 保夫 勝井 義雄 河内 晋平 渡辺 暉夫 藤林 紀枝 前田 仁一郎 柴田 知之 後藤 芳彦 大和田 正明 山崎 哲良 加々美 寛雄

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

巻号頁・発行日

vol.1989, no.1, 1989-04-06

著者

町田 洋 早川 由紀夫 森脇 広 Blong Russell Talai Benjamin

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

巻号頁・発行日

vol.1989, no.2, 1989-10-08

著者

田中 康裕

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.44, no.2, pp.109-110, 1999-04-30

著者

佐藤 鋭一 和田 恵治

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

巻号頁・発行日

vol.2004, 2004-10-19

著者

和田 恵治 中村 瑞恵 奥野 充 佐藤 鋭一

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

巻号頁・発行日

vol.2003, 2003-10-11

被引用文献数

1

著者

大野 希一 国方 まり 鈴木 正章 西村 裕一 長井 大輔 遠藤 邦彦 千葉 達朗 諸星 真帆

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.47, no.5, pp.619-643, 2002-11-29

被引用文献数

4

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The volcanic activities of the Usu 2000 eruption were monitored and reported by many scientists and the mass media. Summarizing these observation results, most of relatively large explosion events occurred during March 31 to April 7, 2000. Around the Nishiyama and Kompira crater groups, the pyroclastic deposits with multi units can be divided into 19 layers on the basis of their visible color, grain size and sedimentary structure; from Layer A to Layer S in ascending order. The eruptive dates of each layer inferred from the wind directions, the eruptive sequence, and the distribution of deposits are summarized as follows; the Layer A, characterized as the light gray color ash fall deposit including in some pumice layers, was generated by March 31 phreatomagmatic explosions occurred at Nishiyama crater group. The Layer B, composed poorly sorted breccia and ash layer with gray color, was generated on March 31 p.m. at Nishiyama craters. The Layer C to the Layer G, dark brown-gray aggregate ash, were derived from the volcanic eruptions occurred on April 1 to 2 in Nishiyama and Kompira crater group. The Layer H to Layer M and Layer O, mainly consist with gray and reddish brown aggregate ash including in lithic fragments, were generated during April 3 and 4 in Kompira crater group. The Layer N, which distributes around N19 crater, generated on April 4. The Layer P, massive ash with gray color, was generated on April 6 in Kompira crater group. After April 7, the Layer S, characterized as light brown aggregate ash, has been generated from the recent minor activities around limited craters. The amount of Layer A fallen in the range from the source to Toyako Onsencho Town is estimated at 1.2×10^8 kg, and total amount of Layer A including in the distal area is 2.4×10^8 kg. On the other hand, amount of other deposits generated during April 1 to 6 (e.g. Layer B, N, and Q) is an order of 10^6-10^7 kg. Total amount of the pyroclastic deposits erupted from the Usu 2000 eruption is more than 6.4×10^8 kg.

著者

周藤 正史 宇都 浩三 味喜 大介 石原 和弘

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

巻号頁・発行日

vol.2001, no.2, 2001-10-01

著者

福島 大輔 小林 哲夫

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

巻号頁・発行日

vol.1996, no.2, 1996-11-05

著者

水田 敏夫 小畑 正明 江上 桂子

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.249-262, 1990-07-02

被引用文献数

3

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Morphology, abundance and vertical distribution of vesicles were studied in a thick (40-60 m) andesitic lava flow, that lies in the underground of Kumamoto City. The vesicles are frozen bubbles that were fomed in the molten lavas at the time of its eruption. The lava can be divided into three zones: (1) an upper vesicular zone (2) a middle non-vesicular and compact zone and (3) a lower, thinner vesicular zone. The vesicles in the upper zone are elongated vertically, probably due to bouyancy-driven ascent of the bubbles, and those in the lower zone are flattened and elongated horizontally, that may be ascribed to a viscous shear flow at the bottom of the lava flow. Size distribution of the vesicles typically display nearly the log-normal distribution. Abundance, the mean size and the number density of the vesicles are greater in the upper zone than in the lower zone. Such vesicle distribution pattern is consistent to the hypothesis that the lava originally contained abundant bubbles when it was poured on the ground and then the bubbles started to ascent in the lava. Vesicles in the lower zone were the bubbles trapped by the advancing cooling front from the bottom surface of the lava. Bubbles that have escaped from the cold trap below have been accumulated in the upper zone and have been frozen in the lava upon cooling from the top surface. Mass balance calculation, however, indicates that much of the bubbles that were originally present in the lava, have been escaped through the lava surface. A dynamic cooling model was, therefore, proposed, that is to say, in the presence of surface flow in the lave during its cooling, impermeable lava crusts may not be maimtained so that gas bubbles may leak out of the lava into the air.