著者

下司 信夫 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.51, no.1, pp.1-20, 2006-02-28

被引用文献数

2

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Volcanic history of Kuchinoerabujima Volcano in the last 30,000 years is reconstructed based on tephra stratigraphy. Kuchinoerabujima is a volcanic island which is a cluster of at least nine volcanic edifices; Gokyo, Jyogahana, Ban-yagamine, Takadomori, Noike, Kashimine, Hachikubo, Furutake and Shintake. Eruptions within the last 30,000 years occurred from Noike, Hachikubo, Furutake and Shintake volcanoes. Two major pumice and scoria eruptions occurred between 15 and 11 ka after an inactive period since ca. 30ka. NoikeYumugi tephra (15-14ka, DRE>0.06km^3), erupted from the summit of Noike Volcano, consists of Yumugi pumice fall deposit and Nemachi pyroclastic flow deposit. Furutake-Megasaki tephra (12-11 ka, DRE ca. 0.8km^3) erupted from Furutake Volcano and consists of Furutake agglutinate, Furutake scoria flow deposit and Megasaki scoria fall deposits. Volcanic edifice of Older Furutake was built during the 12-11 ka eruption. Eruption style changed around 10ka, after the collapse of Older Furutake Volcano. Activities of Yougner Furutake and Shintake Volcanoes are characterized with effusion of lava flow and no major pumice eruption is recognized. Lithic tephra erupted from Younger Furutake and Shitake Volcanoes within the last 10,000 indicates repetitive Vulcanian-type and phreatomagmatic eruptions. All historical eruptions since 1841 occurred at and around Shintake crater and were Vulcanian-type explosions with emission of magmatic materials and phreatic explosions.

著者

森脇 広 小林 哲夫

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.41, no.4, pp.223-224, 2002-08-01 (Released:2009-08-21)

参考文献数

10

被引用文献数

1

著者

井村 隆介 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.36, no.2, pp.135-148, 1991-07-15 (Released:2017-03-20)

被引用文献数

8

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This paper presents results of geologic investigation of the eruptive activity in the last 300 years of Shinmoedake, an active volcano in the Kirishima Volcano Group. The recent activity of this volcano is divided into four eruptive episodes : the 1716-1717, 1771-1772, 1822 and 1959 episodes. The most important activity occurred in 1716-1717. During the 1716-1717 eruption, fallout deposits, pyroclastic flows and mudflows were widely dispersed around the volcano. The products of this episode show that the eruption progressed with time from phreatic to magmatic. These field data are in good agreement with historic records of eruptive activity. According to the historic records, the eruptive activity lasted from 11 March, 1716 to 19 September, 1717. The 1771-1772 and 1822 activities produced base surges, pyroclastic flows, fallout tephra and mudflows that were confined to the slope and eastern base of the volcano, but historic records do not reveal the details of these eruptions. The field evidence shows the same phreatic to magmatic sequence as the 1716-1717 activity. However, the eruptions of both episodes were on a smaller scale than the 1716-1717 eruption. The 1959 activity was well described. This episode produced minor gray silty to sandy lithic fallout tephra indicating that only phreatic activity occurred. The fallout was distributed northeast of the vent. In conclusion, the field evidence and historical records show that each eruptive episode of the current activity of Shinmoedake progressed from phreatic to magmatic. The eruptions are frequently accompanied by pyroclastic flows and mudflows.

著者

小林 哲夫 奥野 充 長岡 信治 宮縁 育夫 井口 正人 味喜 大介

出版者

京都大学防災研究所

雑誌

京都大学防災研究所年報. B = Disaster Prevention Research Institute Annuals. B (ISSN:0386412X)

巻号頁・発行日

vol.53, no.B, pp.269-276, 2010-06-01

著者

井村 隆介 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.36, no.2, pp.135-148, 1991

被引用文献数

16

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This paper presents results of geologic investigation of the eruptive activity in the last 300 years of Shinmoedake, an active volcano in the Kirishima Volcano Group. The recent activity of this volcano is divided into four eruptive episodes : the 1716-1717, 1771-1772, 1822 and 1959 episodes. The most important activity occurred in 1716-1717. During the 1716-1717 eruption, fallout deposits, pyroclastic flows and mudflows were widely dispersed around the volcano. The products of this episode show that the eruption progressed with time from phreatic to magmatic. These field data are in good agreement with historic records of eruptive activity. According to the historic records, the eruptive activity lasted from 11 March, 1716 to 19 September, 1717. The 1771-1772 and 1822 activities produced base surges, pyroclastic flows, fallout tephra and mudflows that were confined to the slope and eastern base of the volcano, but historic records do not reveal the details of these eruptions. The field evidence shows the same phreatic to magmatic sequence as the 1716-1717 activity. However, the eruptions of both episodes were on a smaller scale than the 1716-1717 eruption. The 1959 activity was well described. This episode produced minor gray silty to sandy lithic fallout tephra indicating that only phreatic activity occurred. The fallout was distributed northeast of the vent. In conclusion, the field evidence and historical records show that each eruptive episode of the current activity of Shinmoedake progressed from phreatic to magmatic. The eruptions are frequently accompanied by pyroclastic flows and mudflows.

著者

筒井 正明 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.67, no.1, pp.21-30, 2022-03-31 (Released:2022-04-26)

参考文献数

37

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Ohatayama and Ohataike are adjacent volcanoes aligned in NE-SW direction at the northeastern portion of Kirishima Volcano Group, Kyushu, Japan. Ohatayama volcano has three small craters around the summit area, and Ohataike has a summit crater lake with a diameter of 400 m. Both volcanoes are composed mainly of tephra fall deposits by plinian or sub-plinian eruptions, with intercalations of pyroclastic flow deposits. The main volcanic edifice of the highest point of Ohatayama volcano was formed at least 22 cal ka BP. Tsukiyama were formed earlier than the highest point, and there is a possibility that they can be separated from the highest point. The triangulation point of Ohatayama volcano started its activities on the highest point somewhere around 17-11 cal ka BP, and forming craters A and B. Ohataike volcano was formed by erupting again around 17-11 cal ka BP, after the main volcanic edifice was formed during around 22-17 cal ka BP on the northeast side of the triangulation point. This was followed by four different modes of eruption at Ohatayama C crater in the following order: a phreatic eruption (Oy-4) in 7.6 cal ka BP, Ohatayama lava emission, magmatic and phreatic eruptions (Oy-3) in 7.1 cal ka BP, magmatic and phreatic eruptions (Oy-2) in 6.8 cal ka BP, and lastly, phreatic eruption (Oy-1) in 6.5 cal ka BP. Although no volcanic activity occurred from Ohataike volcano since 11 cal ka BP, foamy volcanic gas is currently being detected on the surface of the crater lake.

著者

石原 和弘 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. 第2集 (ISSN:04534360)

巻号頁・発行日

vol.33, no.3, pp.269-271, 1988-10-31

被引用文献数

2

著者

井口 正人 竹林 幹雄 福島 大輔 中道 治久 小林 哲夫 岩松 暉 幸福 崇 田嶋 祐哉 黒岩 賢彦 上林 嵩弘 三田 和朗

出版者

日本自然災害学会

雑誌

自然災害科学 (ISSN:02866021)

巻号頁・発行日

vol.38, no.3, pp.279-345, 2019

著者

横瀬 久芳 佐藤 創 藤本 悠太 Maria Hannah T. MIRABUENO 小林 哲夫 秋元 和實 吉村 浩 森井 康宏 山脇 信博 石井 輝秋 本座 栄一

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.119, no.1, pp.46-68, 2010-02-15 (Released:2010-05-21)

参考文献数

80

被引用文献数

7 20 1

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To understand the submarine volcanism surrounding the Tokara Islands, a submarine topographic analysis and 67 dredge samplings were carried out. Prior to the submarine investigations, we reviewed comprehensively geological and geophysical data on this region and confirmed the complexity of both volcanic activity and tectonic setting of the Tokara Islands. In contrast to the homogeneous subaerial volcanic rocks comprising predominantly two-pyroxene andesite lava flows, the dredged samples vary from basaltic andesite to rhyolite in composition. Furthermore, we reveal that dacitic and rhyolitic pumices are abundant and broadly distributed throughout the submarine area. The recovered volcanic rocks were mainly subangular to angular cobble-boulder fragments of lava, scoria, and variably vesiculated pumice. Volcanic rocks with hornblende phenocrysts occur only north of the Tokara strike-slip fault, which is a major tectonic element of volcanism. The pumices can be classified into three categories based on the size and abundance of the phenocrysts: aphyric pumice, fine-grained porphyritic pumice, and coarse-grained porphyritic pumice. Occurrences, such as amount in a dredge, shape without extensive abrasion, large fragment size, and bulk rock chemical compositions of the major pumice fragments suggest that they are in situ, rather than originating as drifted pumice or air fall, exotic pyroclastic fragments derived from the four super-eruptions of Kyushu Island. Because dredged samples contained fresh volcanic glass in the groundmass, and are not covered by iron-manganese oxide crust, they appear to have originated from the Quaternary eruptions. Indeed volcanic islands have developed above the submarine erosional terraces (indicated as knick points at approximately 110 m in depth), which is assumed to have formed during the last glacial age. K-Ar age dating on the representative pumice samples resulted in ages of 0.60 ± 0.20 Ma and < 0.2 Ma, respectively. These newly obtained submarine data support that acidic volcanisms occurred around the submarine calderas during the Mid-Pleistocene age.

著者

田島 靖久 松尾 雄一 庄司 達弥 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.59, no.2, pp.55-75, 2014-06-30 (Released:2017-03-20)

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The Kirishima volcanoes located in southern Kyushu are comprised of more than 20 volcanic edifices. The volcanoes occupy an elliptical area of approximately 330km2 with the WNW-ESE direction. Among the different types of volcanic edifices, the typical ones are compound maars and lava flows in Ebinokogen. We studied the volcanic history of Ebinokogen by geological examination of tephra layers and lava flows. After the Karakunidake-Kobayashi plinian eruption, seven tephra were formed in this area. We determined the ages of those tephra and two lava flows. The magmatic eruptions, produced Tamakino B tephra, occurred after Karakunidake-Kobayashi tephra eruption. The first activity in Ebinokogen from about 9.0 cal ka BP generated Fudoike lava flow, and Fudoike-Tamakino A tephra erupted from Fudoike crater. Karakunidake north-Ebino D tephra was generated from the northwest flank of Karakunidake at 4.3 cal ka BP, with debris avalanche and lahars. Phreatic Fudoike-Ebino C tephra erupted from the Fudoike crater at 1.6 cal ka BP. Ioyama-Ebino B tephra eruption started from around the 16th to 17th century with lava flow. Phreatic Ioyama east-Ebino A tephra erupted from Ioyama east crater in 1768 AD. The Ebinokogen area is one of the active regions of Kirishima volcanoes explicated by geophysical observations. Our results indicate cyclical tephra depositions mainly produced by small magmatic and strong phreatic eruptions in this area after the Karakunidake-Kobayashi pyroclastic eruption. Furthermore, the vent locations were found to migrate with each eruption.

著者

小林 哲夫

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.123, no.5, pp.309-319, 2017-05-15 (Released:2017-07-25)

参考文献数

43

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口永良部島・新岳では,2014年8月と2015年5・6月に爆発的な噴火が発生した.噴出物中には新鮮な火山ガラスが含まれていたため,マグマ水蒸気噴火ないしマグマ噴火で,火砕流が発生したと報道された.しかし新鮮な物質は非発泡で,石基はほぼ結晶質であったため,マグマが火道中で固結した貫入岩体の破片と推定された.類似した噴出物の代表例は,1966年の爆発的噴火で放出された高温のジョインテッドブロックである.これら岩塊も高温の岩脈が破砕され噴出したものと判断される.爆発の原因は高温岩体と地下水が反応した蒸気爆発と推定され,噴火メカニズムは水蒸気噴火と酷似していた.新岳の歴史時代の爆発的噴火でも,今回と同じような高温の固結岩塊を噴出した事例が多いかもしれない.なお火口から斜面方向に噴出した噴煙はブラストであったと判断できる.2015年噴火のブラストは,100km/h以上の高速で海岸に達した.

著者

筒井 正明 奥野 充 藤沢 康弘 小林 哲夫 Tsutsui Masaaki Okuno Mitsuru Fujisawa Yasuhiro Kobayashi Tetsuo

出版者

福岡大学研究推進部

雑誌

福岡大学理学集報 = Fukuoka University Science Reports (ISSN:0386118X)

巻号頁・発行日

vol.49, no.2, pp.89-97, 2019-09

著者

小林 哲夫

出版者

日本関節病学会

雑誌

日本関節病学会誌 (ISSN:18832873)

巻号頁・発行日

vol.36, no.2, pp.97-101, 2017 (Released:2018-07-31)

参考文献数

29

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Bacteremia occurs through the translocation of oral bacteria from subgingival biofilms into the systemic circulation following daily oral hygiene activities and dental procedures. Bacteremia is caused more frequently in the treatment of periodontal disease than in other dental procedures. Periodontal treatment involves mechanical debridement, which consists of plaque control, scaling and root planing, and periodontal surgery. The debridement of bacterial biofilms in close proximity to the ulcerated epithelium of the gingival sulcus or periodontal pocket may lead to bacteremia. Therefore, it is essential to maintain oral hygiene and periodontal health in order to decrease the risk of bacteremia. It has long been debated by the American Academy of Orthopaedic Surgeons (AAOS) and the American Dental Association (ADA) whether or not the risk of prosthetic joint infection (PJI) is related to bacteremia after professional dental treatments. Currently, there is strong evidence of such an association. In addition, the indirect evidence obtained from multiple moderate-strength studies suggests that the use of prophylactic antibiotics reduces the incidence of post-dental procedure bacteremia. However, there have been no studies regarding the relationship between bacteremia and PJI. In summary, it is necessary to consider the risk of dental procedure-induced bacteremia and patient characteristics when prescribing prophylactic antibiotics for patients with prosthetic joints who are undergoing dental procedures. It may be particularly beneficial for these patients to maintain good oral hygiene.

著者

小林 哲夫 早川 由紀夫 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.28, no.2, pp.129-139, 1983-07-01

被引用文献数

6

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大隅降下軽石堆積物は, 約22, 000年前に鹿児島湾最奥部で起こった一連の巨大噴火の最初期のプリニアン噴火の産物である.灰白色の軽石と遊離結晶および少量の石質岩片からなる本堆積物は, 全層にわたってほぼ均質な見かけを呈するが, 多くの場合, 上方に向かって粒径がやや大きくなる逆級化層理を示す.層厚分布図(Fig.3)と3種の粒径分布図(軽石の平均最大粒径・石質岩片の平均最大粒径・堆積物の中央粒径;Figs.5, 6, 7)は, いずれも本堆積物の噴出火口が姶良カルデラの南縁, 現在桜島火山の位置する地点付近にあったことを示している.分布軸は火口からN120°E方向に伸びるが, 分布軸から60 km以上離れた地点にも厚く堆積している.又, 堆積物は分布軸の逆方向すなわち風上側にも20 km以上追跡できる.分布軸上で火口から30 km離れた地点での層厚は10 mに達するが, 40 km地点より遠方は海域のため層厚値は得られない.そのため噴出量の見積もりには多くの困難が伴うが, すでに知られている他のプリニアン軽石堆積物の層厚-面積曲線(Fig.4)にあてはめて計算すると, 総体積98 km^3(総重量7×10^<16>g)が得られ, 本堆積物は支笏-1軽石堆積物(116 km^3)に次ぐ最大規模のプリニアン軽石堆積物であることがわかる.3種の粒径分布図から得られる粒径-面積曲線(Fig.8)は, 噴出速度・噴煙柱の高さ・噴出率などで示される噴火の「強さ」を比較する上で有効である.それにより, 大隅降下軽石噴火の「強さ」はけっして例外的なものではなく, プリニアン噴火の平均あるいはそれをやや上回る程度であったことが判明した.

著者

國武 絵美 小林 哲夫

出版者

日本マイコトキシン学会

雑誌

マイコトキシン (ISSN:02851466)

巻号頁・発行日

vol.66, no.1, pp.85-96, 2016-01-31 (Released:2016-02-16)

参考文献数

91

被引用文献数

1

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糸状菌は植物バイオマス(リグノセルロース)に由来する低分子の糖を細胞表層であるいは細胞内に取り込んだ後に感知し,シグナル伝達機構を介してセルラーゼやヘミセルラーゼ遺伝子の発現を転写レベルで活性化する.一方,資化しやすいグルコース等の糖の存在時にはカーボンカタボライト抑制機構が働き,転写が抑制される.このメカニズムを理解することは植物バイオマス分解酵素の効率的な生産に極めて重要である.主にAspergillus属,Trichoderma reesei,Neurospora crassaにおいてゲノムワイドな解析が行われ,遺伝子破壊株ライブラリの利用やセルラーゼ遺伝子と同時に制御される未知遺伝子の機能解析などにより,複数の転写制御因子が単離された.またその上流のシグナル伝達カスケードについても研究が進められており,セルロース性シグナルに対する応答が光や既存の調節経路により微調整されることなども示されている.このレビューではリグノセルロース分解酵素遺伝子の発現制御に関わる転写因子の機能,誘導物質の認識及びそのシグナルの伝達などの遺伝子発現誘導メカニズムに関する研究を概括した.

著者

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.67, no.3, pp.335-350, 2022-09-30 (Released:2022-10-27)

参考文献数

90

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In the Kikai caldera, a major caldera-forming eruption, the Akahoya eruption (Ah eruption), occurred at 7.3 cal ka BP. It started with a plinian eruption (K-KyP), accompanied by a small intra-plinian Funakura pyroclastic flow (K-Fn). In the second eruptive stage, large Koya pyroclastic flow eruption (K-Ky) occurred, which covered the southern part of Kyushu with widespread co-ignimbrite ash (K-Ah (c)). These series of pyroclastic materials are collectively called Kikai-Akahoya tephra (K-Ah (T)). It has been thought that the Akahoya tsunami (Ah tsunami), occurred in connection with the Ah eruption. However, in outcrops below 50 m elevation in the proximal area of the caldera (~60 km), the K-Ah (T) was either replaced by Ah tsunami deposits of various sedimentary facies or completely eroded away by the same tsunami. The largest tsunami was therefore estimated to be due to the collapse of the caldera rim, which occurred some time after the end of the Ah eruption. On the other hand, in the Yokoo midden at Oita city, approximately 300 km from the caldera, it was considered that the K-Ah (c) was deposited immediately above the sandy tsunami deposit. However, the parent material of these distal Ah tsunami deposit is presumed to be K-Ah (r), which was transported and deposited from hinterland to the estuary, and was then incorporated and redeposited by the subsequent striking Ah tsunami. That is, the particles in the tsunami can be interpreted as separating and settling into two different layers, i.e. the basal sand layer and the upper K-Ah (r) set as the same tsunami deposit, due to differences in density. This interpretation is also supported by the chemical analyses of volcanic glass. Thus, the erosion and deposition either proximal or distal area of the caldera indicate that the largest Ah tsunami occurred some time after the Ah eruption. The caldera rim shows a double depression structure which was formed during the Ah eruption, and there are many channel structures on the caldera rim that suggest intense seawater movement. It is therefore highly probable that the sudden collapse of caldera wall after the Ah eruption is the cause of the tsunami, together with the run-up height near the caldera. However, it is not possible to estimate the time until the collapse that caused the Ah tsunami.

著者

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 2016 (ISSN:24335320)

巻号頁・発行日

pp.101, 2016 (Released:2017-02-07)

著者

小林 哲夫 佐々木 寿

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.120, no.Supplement, pp.S63-S78, 2014-08-31 (Released:2014-12-26)

参考文献数

57

被引用文献数

3

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桜島火山は鹿児島湾最奥部を占める姶良カルデラの後カルデラ火山であり,その誕生は26,000年前である.歴史時代にも多くの噴火を繰り返したが,ちょうど100年前の大正噴火(1914年)で流出した溶岩で瀬戸海峡が埋め立てられ,大隅半島と陸続きとなったのは有名である.その後も山頂~山頂付近に生じた火口で活発な噴火活動を続けており,日本を代表する活火山である.本コースでは,桜島火山の歴史時代の噴出物や最新の火山地形を観察する.特に大正噴火の西側火口から噴出した火砕物質と溶岩流の産状を詳しく観察し,噴火の推移を考える.

著者

長井 雅史 小林 哲夫

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.124, no.1, pp.65-99, 2015-02-25 (Released:2015-03-11)

参考文献数

43

被引用文献数

10 11

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Ioto (Iwo-Jima; Sulphur Island) is a volcanic island located at the volcanic front of the Izu-Bonin arc about 1250 km south of Tokyo. The island consists of a central cone and southwest rim of a submarine caldera with a diameter of about 10 km. The rocks of the volcano are trachyandesite and trachyte, which are seldom found at a volcanic front. High rates of geothermal activity and crustal uplift have been observed, which are considered to be related to magma intruding at a shallow depth. Therefore, Ioto volcano is considered to be an active resurgent dome. However, eruptive history, including the process and timing of caldera formation, has not been clarified. Eruptive history based on our recent field survey, dating, and chemical analysis is as follows. A pre-caldera edifice was formed by volcanic activity of trachyandesite-trachyte magma in a subaerial and subaqueous environment. The magma composition and types of eruption were similar to those of the post-caldera edifice. It is still unclear when the caldera was formed. The caldera floor, which was a sedimentary basin with shallow marine sediments and a subaqueous lava flow, has been present at least since 2.7 cal kBP. Furthermore, a small volcanic island covered with trees used to exist in the Motoyama area. The complicated sequence of the Motoyama 2.7 cal kBP eruption is described as follows. First, on the volcanic island or in the surrounding shallow water, an explosive phreatomagmatic eruption occurred that formed subaqueous welded tuff (Hinodehama ignimbrite) and a subsequent thick subaqueous lava flow (Motoyama lava). While the Motoyama lava was still hot, the eastern part collapsed. The collapsed mass was quenched to form large blocks similar to pillow lava. A subsequent large phreatomagmatic eruption occurred, destroying the hot Motoyama lava, the older edifice, and the marine sediment. The resultant subaqueous pyroclastic flow generated the Motoyama pyroclastic deposit. Then, the eruption center shifted to the Suribachiyama area, which is just outside the southwest caldera rim. Deposits from three different eruption periods have been identified—lower, middle, and upper pyroclastic deposits—and a lava flow that erupted during the middle pyroclastic period. The lower unit was formed by a subaqueous eruption at a deeper level; the middle deposit was formed by a phreatomagmatic explosion at a shallow depth; and, the following lava emission generated a lava island. The upper pyroclastic deposit was generated by a combination of phreatomagmatic and Strombolian eruptions. Although the ages of these eruptions are not obvious, the first phase of the eruption occurred during the period between 2.7 cal kBP and 0.8-0.5 kBP, which is estimated from the age of the upper marine terrace X (Kaizuka et al., 1983). The eruption of the upper deposit occurred before AD 1779 (ca. 0.2 kBP). The eruptive products described so far are covered with younger sediment from marine terraces and spits. Recently, small-scale deposits from phreatic explosions accompanied by geothermal and uplift activities have been found distributed throughout the island, but juvenile material has not been confirmed to exist in the products.

著者

田島 靖久 及川 純 小林 哲夫 安田 敦

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.67, no.1, pp.45-68, 2022-03-31 (Released:2022-04-26)

参考文献数

105

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Shinmoedake is the compound volcano in Kirishima Volcano and the most active volcano in Japan, having recorded frequent magmatic eruptions during 1716-1717, 2011, and 2018. The three geological active periods of Shinmoedake in the last 8 ka were recorded by a geological survey (Tajima et al., 2013a). The geological eruptive time category of Shinmoedake is divided into long-term, middle-term, and short-term activities. Short-term activity is captured by monitoring and covers a period of several years or more. The magma eruption rates during middle-term activities were estimated to be several times higher than the long-term magma eruption rate. Moreover, the centers of magma eruptions within each middle-term period had stabilized in terms of location. Additionally, the magma eruption rates during each period of middle-term activity were not constant. Therefore, knowledge regarding the variation in the magma production of Shinmoedake during geologically short-term, middle-term, and long-term activities is required to understand its development and plumbing system. In this paper, we compile recent geological investigation results of Shinmoedake and propose a rational conceptual model of its current state supported by petrological and geophysical data. A well-known conceptual plumbing model of Kirishima Volcano was proposed by Kagiyama et al. (1997). The seismic attenuation spot (reservoir A) is located at a depth of 4-5 km below Karakunidake (Oikawa et al., 1994), and a wide P-wave velocity anomaly area (reservoir W) is situated at a depth of 10-15 km below Kirishima Volcano (Yamamoto and Ida, 1994). Recently, geophysical observations have indicated that magma was supplied from a depth of 8-10 km (reservoir B) to the western area of Shinmoedake during the 2011 magmatic eruption (Nakao et al., 2013). In addition, petrological analysis suggested two different sources of silicic magma from a level of reservoir A and mafic magma from a level of reservoir B (Suzuki et al., 2013a). Therefore, reservoir B might have been connected to reservoir A, where magma mixing occurred during the 2011 eruption. Furthermore, analysis of the deep low-frequency (DLF) earthquake of the 2011 eruption of Shinmoedake revealed that the DLF activities at a depth of 20-27 km (reservoir L1) in the eastern part of Kirishima Volcano were involved (Kurihara et al., 2019). Reservoirs L1 and B may also be connected. These results support the increasing activities of Kirishima Volcano revealed by the geological survey (Tajima et al., 2013a). It is concluded that the complex magma plumbing system of Shinmoedake may cause different magma eruption rates during periods of middle- and long-term activities.