157 results on '"ISHIHARA, Kazuhiro"'
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2. Doublet or Triplet Antiemetic Prophylaxis for Nausea and Vomiting Induced by Trastuzumab Deruxtecan: an Open-Label, Randomized, and Multicenter Exploratory Phase 2 Study
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Iihara, Hirotoshi, primary, Shimokawa, Mototsugu, additional, Bando, Hiroko, additional, Niwa, Yoshimi, additional, Mizuno, Yutaka, additional, Kawaguchi, Yoshihiro, additional, Kitahora, Mika, additional, Murakami, Akari, additional, Kawai, Masaaki, additional, Ishida, Kazushige, additional, Takeuchi, Makoto, additional, Ishihara, Kazuhiro, additional, Iyoda, Tomokazu, additional, Nakada, Takumi, additional, Ogiso, Atsuko, additional, Kojima, Yasuyuki, additional, Kumagai, Fumiyoshi, additional, Sawa, Aya, additional, Mori, Ryutaro, additional, Higuchi, Kosuke, additional, Furuta, Tomoko, additional, Kamei, Yoshiaki, additional, Tsuchiya, Masami, additional, Terasaki, Azusa, additional, Yamamoto, Senri, additional, Kitazawa, Mai, additional, Okazaki, Mai, additional, Suzuki, Akio, additional, and Futamura, Manabu, additional more...
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- 2023
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Catalog
3. Subtle changes in strain prior to sub-Plinian eruptions recorded by vault-housed extensometers during the 2011 activity at Shinmoe-dake, Kirishima volcano, Japan
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Yamazaki, Ken’ichi, Teraishi, Masahiro, Ishihara, Kazuhiro, Komatsu, Shintaro, and Kato, Koji
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- 2013
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4. Analysis of pressure waves observed in Sakurajima eruption movies
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Yokoo, Akihiko and Ishihara, Kazuhiro
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- 2007
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5. Behavior of fluorine and chlorine in volcanic ash of Sakurajima volcano, Japan in the sequence of its eruptive activity
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Nogami, Kenji, Iguchi, Masato, Ishihara, Kazuhiro, Hirabayashi, Jun-ichi, and Miki, Daisuke
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- 2006
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6. Cryptogenic organizing pneumonia after radiotherapy for breast cancer
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Akita, Kenji, Ikawa, Aiko, Shimizu, Shigeki, Tsuboi, Kazuya, Ishihara, Kazuhiro, Sato, Shigeki, and Ueda, Ryuzo
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- 2005
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7. Reexamination of moment tensors for initial motion of explosion earthquakes using borehole seismograms at Sakurajima volcano, Japan
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Tameguri, Takeshi, Iguchi, Masato, and Ishihara, Kazuhiro
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- 2001
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8. Evaluation of hydroxyapatite-coated screws for lumbar spine fixation in dogs
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Matsuzaki, Hiromi, Numabe, Tomohiro, Tokuhashi, Yasuaki, Wakabayashi, Ken, Ishihara, Kazuhiro, Shirasaki, Yoshio, and Tateishi, Tetsuya
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- 1997
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9. Evaluation of cylindrical interbody fusion devices in canine lumbar spine: Comparison of fixation stiffness in devices with and without hydroxyapatite coating
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Matsuzaki, Hiromi, Tokuhashi, Yasuaki, Wakabayashi, Ken, Ishihara, Kazuhiro, Ishikawa, Hiroto, Okawa, Akihiro, Shirasaki, Yoshio, and Tateishi, Tetsuya
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- 1997
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10. Cryopreserved intervertebral disc allografts in dogs: Chronological changes in 3-year period after transplantation
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Ishihara, Kazuhiro, Matsuzaki, Hiromi, and Wakabayashi, Ken
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- 1996
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11. Understanding of Volcanic Phenomena and Prediction of Volcanic Eruptions
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ISHIHARA, Kazuhiro
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prediction of volcanic eruptions ,mitigation of volcanic hazards ,hazard map ,火山防災 ,volcanic alert ,火山噴火予知 ,519.9 ,噴火警報 ,ハザードマップ - Abstract
1974年に開始された火山噴火予知計画の狙いと計画実施の特色,研究成果および火山防災との関連について概説した。地下のマグマの動きを種々の観測で捉えることが噴火予知につながり,研究観測成果を気象庁の業務に活かすことにより噴火予知の実用化を図るという当初計画の趣旨にそって,火山噴火予知計画は遂行され,噴火予知実用化の第一歩である噴火予警報が2007年に開始された。また,火山学の成果や火山学的知見は,ハザードマップ作成や火山危機時の助言など火山防災にも活かされている。, This manuscript describes the outline of the National Project of Prediction of Volcanic Eruptions (1974-2008): scientific and social purposes and results. Several methods and instruments developed under the project and scientific knowledge on volcanic activities were transferred to the Japan Meteorological Agency, which started a quantitative volcanic alert in December 2007. Volcanologists have contributed to mitigation of volcanic hazards in various aspects, making of volcanic hazard maps and evacuation plans, and as experts in volcano crisis, based on scientific research and experiences of volcano crises at several volcanoes. more...
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- 2012
12. Age of Lava Flows in Southwestern Slope of Minamidake, Sakurajima Volcano, Inferred from Paleomagnetic and Chemical Features
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MIKI, Daisuke, UTO, Kozo, HOANG, Nguyen, and ISHIHARA, Kazuhiro
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全岩化学組成 ,historic eruption ,桜島火山 ,paleomagnetical age estimate ,歴史時代の噴火 ,chemical composition ,519.9 ,古地磁気学的年代推定 ,Sakurajima volcano - Abstract
桜島火山南岳南西斜面の持木川河岸に分布する溶岩流について古地磁気測定および全岩化学組成分析を行った。その結果,9世紀後半から11世紀前半の古地磁気学的推定年代を得た。このことはこれまで知られていなかった歴史時代の溶岩流出を伴う噴火があったことを示す。また研究地域の一部には文明溶岩と考えられる溶岩が小規模に分布しているが,研究地域南側の海岸に達する文明溶岩の岩体とは連続していないことがわかった。, Paleomagnetic measurements and chemical composition analysis were carried out on lava flows, distributed around southwestern slope of Minamidake, Sakurajima volcano. A paleomagnetic age from most of studied lava flows is estimated as late 9c to early 11c AD. This may show that there is an unknown 'historic' eruption accompanied with lava flow. A lava flow considerable to be Bunmei lava is also found, but distribution of this lava flow may be small and not connected to larger body of Bunmei lava lied at coast area. more...
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- 2012
13. 2010年メラピ火山およびシナブン火山噴火から学ぶ
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IGUCHI, Masato, ISHIHARA, Kazuhiro, SURONO, and HENDRASTO, Muhamad
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水蒸気爆発 ,メラピ火山 ,火山防災 ,pyroclastic flow ,シナブン火山 ,Merapi volcano ,火砕流 ,phreatic eruption ,volcanic disaster prevention ,519.9 ,Sinabung volcano - Abstract
2010年には特筆すべき噴火がインドネシアのシナブン火山とメラピ火山において発生した。これらの噴火活動とその対応から我々は, 次のことを教訓として得た。1)長期の休止後の噴火活動の評価は依然として難しく, 長期の休止期の空白を埋めるための緊急観測が必要である。2)火道最上部が開放した火山での噴火活動の予測はやはり困難を伴う。このような状況では地盤変動観測の高精度化と物質化学的分析が重要となる。3)我が国の火山では火口から20kmにおよぶ警戒区域の設定と38万人にも達する避難者への対応の経験がない。被害区域が拡大した場合の対応を早急に策定する必要があろう。, In 2010, noteworthy eruptions occurred at Sinabung, North Sumatra and Merapi in Central Java, Indonesia. Sinabung volcano erupted on August 27 after dormancy more than 400 years and repeated 7 eruptions till September 7. At Merapi volcano, explosive eruption occurred at the summit on October 26 accompanying resultant blast and pyroclastic flow. The eruptive activity reached at the peak on November 3-5, generating continuous pyroclastic flow which ran southward 17 km in distance. We obtain important lessons from these eruptions for evaluation of volcanic activity and prediction of volcanic eruption. Evaluation of volcanic activity is still difficult at volcanoes after long-term dormant period. Quick response to obtain data is important to compensate the gap from the last eruption. It is difficult to predict activity of volcanoes under the condition of open-conduit system, too. Associated with extension of flow length of pyroclastic flow, restricted zone was extended up to 20 km and 380, 000 people evacuated from Merapi volcano. Japan has not been experienced by risk management for such a large number of evacuees from volcanoes. Countermeasure planning against volcanic eruptions with disaster in wider area should be established. more...
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- 2011
14. Sequence and Characteristics of the 2007 Eruptions at Showa Crater of Sakurajima Volcano
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YOKOO, Akihiko, TAMEGURI, Takeshi, IGUCHI, Masato, and ISHIHARA, Kazuhiro
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2007年噴火 ,桜島 ,単調微動型空気振動 ,519.9 ,the 2007 eruption ,monotonic infrasound tremor ,Showa crater ,Sakurajima volcano ,昭和火口 - Abstract
2007年5月から6月のおよそ40日間にわたって,桜島昭和火口で噴火活動が発生した。2007年噴火初期には,それまで火道内を埋めていたと考えられる比較的低温の灰放出が観測された。第2活動期は,100℃を超える噴煙が頻繁に観測され,初動の立ち上がりが明瞭な,いわゆる爆発型の空気振動を伴う噴火である。赤熱物質の放出や火映が観察されるなど,2007年噴火の活動最盛期であったといえる。噴火活動が終息する直前2週間は,20縲・0℃の低温噴煙が放出され,この現象に対応する空気振動は約1 Hzに卓越周波数を持つ単調微動型であった。, Showa crater of Sakurajima volcano erupted again in 2007 after 1 year's interval. Activity of this 2007 eruptions was able to be divided into three stages. The first stage was characterized by weak ejection of volcanic materials without significant infrasound signals. This stage lasted only for the first few days. Main explosive eruptions accompanying with impulsive infrasound waves occurred in the second stage (about two weeks). During this stage, incandescent reddish ejecta were frequently observed. Temperatures of the eruption clouds were relatively high (~160°C). Final two weeks was categorized into the third stage of the 2007 eruptions. Peculiar infrasound tremor signals (peak frequency was about 1.0 Hz) were recorded associated with minor ash eruptions. more...
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- 2008
15. 熱水流動を考慮した火山地磁気効果の数値シミュレーション(2)
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OKUBO, Ayako, KANDA, Wataru, and ISHIHARA, Kazuhiro
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piezomagnetic effect ,熱水流動 ,マグマ貫入 ,キャップロック ,numerical simulation ,hydrothermal activity ,浸透率 ,シミュレーション ,519.9 ,permeability ,caprock ,ピエゾ磁気効果 - Abstract
マグマ貫入後の熱水流動のシミュレーションを行い,熱水系の消長によって地表でのピエゾ磁場がどのように変化するかを数値的に評価した。シミュレーションで得られる間隙水圧の分布から火山体内部の磁化変化分布を見積もり,地表でのピエゾ磁気変化を計算するポストプロセッサを開発し,浸透率および不透水岩体であるキャップロックがピエゾ磁気変化にどの程度影響を与えるかをケーススタディ化することで調べた。その結果,浸透率が小さい方が,地磁気変化が大きく,地磁気変化が観測される時間が長いこと,またキャップロックが存在する場合は,存在しない場合と比べて地磁気変化が大きくなることがわかった。, Geomagnetic field variations observed at many volcanoes suggest temperature changes and/or stress changes inside those volcanoes. Such volcanomagnetic effects are largely controlled by a behavior of volcanic fluids or hydrothermal systems that transport heat and mass from the deep source. In this study, we have developed postprocessors to calculate piezomagnetic effects caused by hydrothermal pressurization. By using a newly developed postprocessor, we carried out numerical experiments on the effect of host-rock permeability and the influence of caprock, as a factor to change the physical state within the volcanic edifice. From these evaluations, it turns out that the both effects influence not only the amount of piezomagnetic changes but also the duration of the anomalous piezomagnetic field. more...
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- 2007
16. 火山情報と自治体の防災対応 : 2006年桜島噴火の例
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ISHIHARA, Kazuhiro
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volcanic information ,火山災害の軽減 ,危機管理 ,mitigation of volcanic disaster ,火山情報 ,519.9 ,crisis management - Abstract
2006年6月に桜島の中腹の昭和火口から突如噴火がはじまり,約1ヶ月間噴火活動が続いた。火砕流の発生が懸念されたが,ごく小規模なものであった。本稿は,この活動に関連した火山情報と地元関係機関の防災対応について解説している。関係機関の連携のもと円滑な防災対応がなされた背景には,桜島のハザードマップ作成等の共同作業を通じて得られた火山活動に関する知識の共有がある。, In June 2006, eruption abruptly occurred on the eastern slope of Sakurajima volcano, and activity continued for a month. It was anxious that the activity might be accompanied with pyroclastic flows, but the actual flows were minor. This manuscript describes volcanic information and countermeasures done by local authorities related to this short-term volcano crisis. Quick response of local governments and sooth decision of countermeasures among several organizations were achieved under common understanding on volcanic activity. more...
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- 2007
17. 熱赤外カメラとビデオカメラによる2006年桜島昭和火口周辺の火山活動モニタリング
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YOKOO, Akihiko and ISHIHARA, Kazuhiro
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桜島 ,2006年噴火 ,熱赤外映像観測 ,519.9 ,Showa crater ,the 2006 eruption ,infrared thermal observation ,Sakurajima volcano ,昭和火口 - Abstract
2006年6月4日に,桜島東斜面の昭和火口周辺部から噴火活動が始まり,6月20日までのおよそ半月間継続した。今回の噴火活動は間欠的な小規模噴煙放出で特徴付けられ,6月9日以降はごく小規模な火砕サージも発生した。昭和火口周辺を含む桜島南岳の東~南東斜面の熱異常域は、2006年3月にはすでに活発化しており,これは2006年噴火の前兆現象のひとつであった。, The 2006 eruptions around Showa crater which located at the eastern flank of Minamidake, Sakurajima volcano, started on June 4, 2006, after 58 years dormancy. It continued about half a month. This eruption was characterized by the numerous emissions of volcanic slugs with time intervals of 5-30 min. Small scaled pyroclastic surges were observed after June 9 till the end of the eruption. As results of infrared thermal observations during 2006, geothermal activities of eastern to southeastern flank of Minamidake have increased prior to the 2006 eruptions. Still March 2007, no significant changes of thermal activities have been recognized after the eruption. more...
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- 2007
18. Evaluation of Eruption Potential
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ISHIHARA, Kazuhiro
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火山災害 ,桜島 ,eruption potential ,Sakurajima ,volcanic hazards ,中期予測 ,middle-term prediction ,噴火ポテンシャル ,453.8 - Abstract
本稿では,火山噴火の予知と火山災害の軽減にとって火山活動の中期的(数10年)な予測評価が重要であるという認識に立って,噴火ポテンシャルという概念を提示し,それに含まれるべき内容と評価に必要なデータ・知識について論じている.桜島を例として噴火ポテンシャル評価を行い,当面の20年に予想される4つの活動シナリオを示し,噴火にいたる過程で発現する現象,予想される災害と影響範囲を見積もった.噴火ポテンシャル評価が可能の知識・データの蓄積のある火山は多く見積もっても全国で20火山程度であり,その他の火山での評価は困難であり予期せぬ顕著な噴火が発生する可能性が高い., This manuscript proposed a concept ‘eruption potential’ and discussed its contents and data and knowledge necessary for its evaluation. As one example, eruption potential at Sakurajima volcano was shown: possibility of eruption in a few decades, possible styles of eruption, eruption scenarios and expected hazards. In Japan, similar evaluation as Sakurajima might be possible at about 20 volcanoes among 108 active volcanoes. At other volcanoes, it is difficult to evaluate eruption potential. more...
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- 2006
19. Numerical Simulation of Volcanomagnetic Effects due to Hydrothermal Activity
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OKUBO, Ayako, KANDA, Wataru, and ISHIHARA, Kazuhiro
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熱磁気効果 ,熱水流動 ,マグマ貫入 ,numerical simulation ,hydrothermal activity ,浸透率 ,シミュレーション ,permeability ,453.8 ,magma intrusion ,450.12 ,thermomagnetic effect - Abstract
マグマ貫入後の熱水流動のシミュレーションを行い,熱水系の消長によって地表での地磁気がどのように変化するかを数値的に評価した。シミュレーションで得られる温度分布から火山体内部の磁化分布を見積もり,地表での地磁気変化を計算するポストプロセッサーを開発し,マグマの貫入の深さおよび浸透率が地磁気変化に与える影響を調べた。その結果,より浅くマグマが貫入する方が,地磁気変化が大きく,地磁気変化が観測される時間が短いこと,また,浸透率が小さいほうが,地磁気変化が大きく,地磁気変化が観測される時間が長いことがわかった。, We have developed a postprocessor to calculate the geomagnetic field variations caused by hydrothermal activities in the volcanic region. They use distributions of temperature inside the volcano, which are results of a numerical simulation for hydrothermal activity after magma intrusion. The most dominant mechanism of volcanomagnetic effects was considered here: thermomagnetic effect. We examined the influences of host rock permeability and depth of magma intrusion on thermomagnetic effect. Results showed that the shallower depth of intrusion causes larger total intensity anomaly and earlier decline of it and that larger anomalies appear at later times in cases of lower permeability host rocks. more...
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- 2006
20. Seismic Exploration by Using Active Sources at Kuchierabujima Volcano, Southwest Japan
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IGUCHI, Masato, YAMAMOTO, Keigo, HASHIMOTO, Takeshi, TSUTSUI, Tomoki, TANAKA, Satoru, ONIZAWA, Shin'ya, AOKI, Yosuke, WATANABE, Toshiki, OHKURA, Takahiro, SHIMIZU, Hiroshi, YAKIWARA, Hiroshi, MIYAMACHI, Hiroki, HIRAMATSU, Hideyuki, TAMEGURI, Takeshi, TAKAYAMA, Tetsuro, FUKUSHIMA, Masayo, TRIASTUTY, Hetty, ISHIHARA, Kazuhiro, OSHIMA, Hiromitsu, SUZUKI, Atsuo, MAEKAWA, Tokumitsu, KAJII, Tatsuya, WATANABE, Yoshiaki, OGIWARA, Yohei, NOGAMI, Kenji, OIKAWA, Mitsuhiro, HIRABAYASHI, Jun-ichi, TSUJI, Hiroshi, HIRATA, Yasuhiro, OKUDA, Takashi, ITOH, Taku, YOSHIKAWA, Shin, INOUE, Hiroyuki, IKEDA, Sayaka, HORI, Mio, SAITO, Masaki, HIRANO, Shuichiro, UEKAMA, Yudai, IGUCHI, Motoharu, TAKESHITA, Takahiro, and MORI, Takehiko more...
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口永良部島火山 ,人工地震探査 ,火山噴火予知計画 ,Kuchierabujima volcano ,地震波速度構造 ,seismic exploration ,453.8 ,National Project for Volcanic Eruption Prediction ,seismic velocity structure ,453.3 - Abstract
口永良部島火山の浅部構造を明らかにすることを目的として人工地震探査を2004年11月に行った。183点の地震観測点(内3成分75点)を設置し,19点において爆破を行った。初動の読み取りを行った結果,2955個の検測値が得られ,そのうち2187個はAおよびBランクの精度のよいものであった。発破点付近の見かけ速度は近傍の地質構造を強く反映したものであるが,発破点から距離5km付近からは見かけ速度5km/sの屈折波が観測された.新岳・古岳の山体では走時が早い傾向が認められるとともに強い散乱波が観測された。, Seismic exploration using artificial sources was conducted at Kuchierabujima volcano, southwest Japan in November 2004 to investigate subsurface seismic structure. A total of 183 temporal stations equipped with a 2Hz vertical component seismometer (including 75 3-component seismometers) and a portable data logger were deployed. Dynamite shots with charges of 10-115kg were detonated at 19 locations. To reveal shallow structure of the volcano, 2955 arrival times of the first motion were picked from the seismograms and 2187 were classified into ranks A and B. Refracted waves of 5km/s were observed at stations >5 km apart from the shot points. Apparent velocities near the shot points depend on surface geology around the shots. P-wave arrived earlier at stations near the summits. Strongly scattered waves were observed near the summits. more...
- Published
- 2005
21. Automated Classification of Volcanic Earthquakes and Tremors -Outline of the system and preliminary experiment
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ISHIHARA, Kazuhiro, TAMEGURI, Takeshi, and IGUCHI, Masato
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即時自動分類 ,automated classification ,volcanic earthquakes and tremors ,453.5 ,火山性地震 ,火山性微動 - Abstract
火山性地震・微動を即時自動判別するシステムのプロトタイプを作成し,口永良部島火山を対象に試行を行った。分類には,基準観測点の震動継続時間,最大振幅,スペクトルなど波形を特長付けるパラメータに加えて参照観測点との震動開始時刻の差や振幅比を用いている。8ヶ月間の試行では,台風時の擾乱と島外で発生する構造性地震の識別が出来なかった。その原因は,主として,参照観測点の選定が不適切であったことによると考えられる。台風時の擾乱と構造性地震を除けば,ほぼ適切な分類がなされた。, A seismic data processing system for automated classification of volcanic earthquakes and tremors is developed, and preliminary experiment was done using seismic data at Kuchinoerabujima volcano. The outline of the system and the results and evaluation of the preliminary experiment are described. more...
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- 2005
22. Temporal Evolution of Magma Composition in Sakurajima Volcano, Southwest Japan
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UTO, Kozo, MIKI, Daisuke, NGUYEN, Hoang, SUDO, Masafumi, FUKUSHIMA, Daisuke, and ISHIHARA, Kazuhiro
- Subjects
全岩化学組成 ,同位体地球化学 ,Isotope geochemistry ,Magma evolution ,桜島火山 ,453.8 ,Whole rock chemistry ,マグマ進化 ,Sakurajima volcano - Abstract
桜島火山の噴出物について,系統的な全岩化学分析および同位体分析を実施し,マグマの化学組成の時間変化について検討を行った。その結果,最近の約2千年間の南岳噴出物は,それ以前の南岳および北岳噴出物と有意に異なる化学組成を有すること,桜島火山初期噴出物は有史噴出物と類似の組成を有することが判明した.また,時間と共に緩やかに化学組成が変化すること,特に4千年前から文明噴火まではSiO2が増加し,その後は減少したことが明らかになった.これらは,大局的には桜島の誕生以降,姶良マグマ溜まり内の地殻起源珪長質マグマにマントル起源苦鉄質マグマが徐々に注入された結果と判断され,最近の4千年間は次第にマントル起源マグマの割合が徐々に増大していると推定される., Temporal variation of major and trace element chemical compositions along with Sr isotopes were examined for eruptive products from Sakurajima volcano. Products of recent 2, 000 years have higher Ti, P, Zr and Y contents than older ones except for earliest stage eruptives. There are temporal variations in magmatic composition: SiO2 content increased from 4 ka to Bunmei eruption then decreased to the recent, but Zr/Th ratio increased gradually in the past 4, 000 years. Mantle-derived mafic magma has been supplied to the magma chamber beneath the Aira Caldera, and mixed with the crust-derived felsic magma. It is suggested that the supply of mafic magma increased with time in the past 4, 000 years. more...
- Published
- 2005
23. Volcanic Disaster Prevention and Community Development-How to convert the volcano into a museum
- Author
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FUKUSHIMA, Daisuke and ISHIHARA, Kazuhiro
- Subjects
教育 ,NPO ,education ,エコミュージアム ,community ,519.9 ,eco-museum ,まちづくり - Abstract
「災害に強いまちづくり」を行う上で最も重要な課題の一つは、住民が地域の災害リスクを認知できるような環境を整えることだろう。本研究では、地域をまるごと博物館と考えるエコミュージアムのコンセプトを桜島で適用・実践し、その防災効果について検討した。これまで実践の結果、エコミュージアムのコンセプトは防災教育を持続的に行う社会教育システムの一つとして機能することが分かった。また、まちづくりや地域振興の方法の一つとして行政にも注目されつつあり、今後はエコミュージアムのコンセプトを適用した都市計画が策定されるであろう。エコミュージアムの運営は地域住民が主体となる必要があり、NPOなどの存在が重要である。今後はNPO等の組織づくりと運営のための財源確保が重要な課題である。, One of the most vital issues in developing a community resistant to disasters, is to create an environment where inhabitants are aware of the disaster risks of their own region. We are implementing efforts to utilize an eco-museum concept that regards the whole area as a museum. Through our practices, the following points were found. (a) The concept of an eco-museum is an effective measure for conveying the disaster risks of a region. (b) An eco-museum has the expectations of governments to work as a tool for regional development and disaster prevention. (c) In order to implement an eco-museum, the formation of an organization such as an NPO is necessary. Stable management can be developed through collaborated works with governments. more...
- Published
- 2005
24. Behavior of Volatile Components in Volcanic Ash Ejected by Several Types of Volcanic Eruptions at an Andesitic Volcano: Sakurajima, Japan
- Author
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NOGAMI, Kenji, IGUCHI, Masato, ISHIHARA, Kazuhiro, HIRABAYASHI, Jun-ichi, and MIKI, Daisuke
- Subjects
eruption ,火山噴火 ,volatile components ,揮発性成分 ,volcanic ejecta ,火山噴出物 - Abstract
本報では、桜島火山における様式の異なる噴火で放出された火山灰の揮発性成分、特にフッ素と塩素の挙動について噴火活動との関係を検討した。不溶性塩素濃度は,BL型地震を伴う噴火で放出された火山灰が最も高く,爆発によって放出された火山灰との間に統計的に有意の差が認められる。これは,BL型地震の発生は塩素に富んだ新鮮なマグマの火口浅部への上昇によるもので,その群発から爆発に至る過程で塩素の脱ガスが起っていることを示している。, In this study, we determined the contents of F and Cl in the volcanic ash ejected by several types oferuptions of Sakurajima volcano and examined a relationship between the behavior of halogen and theeruptive activity. Statistical examinations reveal that the ash samples collected between 1975 and 2002are categorized into "BL-earthquakes " group and the others according to the contents of water-insolubleCl. This suggests that the swarm of BL-type earthquakes was attributed to ascension of fresh magmafrom the upper part of the conduit to the summit crater and that Cl is degassed between the "Blearthquake"stage and "explosion" stage. more...
- Published
- 2004
25. DOASによって観測された火山ガス放出量の変動について ~桜島・諏訪之瀬島~
- Author
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MORI, Takehiko, ISHIHARA, Kazuhiro, HIRABAYASHI, Junichi, KAZAHAYA, Kouhei, and MORI, Toshiya
- Subjects
火山ガス ,Volcanic gas ,DOASとCOSPEC ,SO2 emission ,SO2 column濃度 ,SO2放出量 ,COSPEC and DOAS ,SO2 column concentration - Abstract
我々は火山からのSO2放出量測定のために,光学的な吸収分光計を用いた試験的な測定機器(DOAS)を新たに開発した。この機器の基本的な動作試験は浅間山や三宅島などの日本の火山で2003年に行われてきた。そして,DOASの特性試験と実際の計測が桜島と諏訪之瀬島(トカラ列島の火山島)で2003年の10月から11月にかけて行われた。桜島では500~1000ton/dayのSO2放出量が記録された。活動が最盛期であった桜島からのSO2放出量の半分以下の計測値であるが,現在の桜島の火山活動の低さから考えると妥当である。また,噴火活動が活発である諏訪之瀬島では初のSO2放出量の測定が行われ,約1000ton/dayのSO2放出量が計測された。桜島最盛期と比べるとSO2放出量は低いが,諏訪之瀬島の噴火規模から考えると妥当な放出量と考えられる。一方で,火口近傍にDOASを運び,SO2 column濃度の時間変動の測定にも成功した。, We have produced trial instrument for measurement of SO2 emission using differential optical absorption spectrometer (DOAS). Its performance has been tested at several volcanoes in Japan since 2003. The performance of the DOAS and its practice measurement were executed in Sakurajima and Suwanosejima. The SO2 emissions from Sakurajima and Suwanosejima were measured by the DOAS. Sakurajima emitted 500~1000ton/day due to dormancy of the volcanic activity. The excellent portability of the DOAS enables to estimate the SO2 emission from Suwanosejima at 1000ton/day. In addition, the DOAS enables to monitor temporal variation in the SO2 column concentration in the vicinity of the crater. We carried out measurement of the SO2 column concentration (ppmm) in the plume at Suwanosejima. more...
- Published
- 2004
26. 火山活動の評価手法の開発と火山防災情報に関する研究(序報)
- Author
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ISHIHARA, Kazuhiro, IGUCHI, Masato, MIKI, Daisuke, YAMAMOTO, Keigo, KANDA, Wataru, TAMEGURI, Takeshi, FUKUSHIMA, Daisuke, MORI, Takehiko, OSHIMA, Hiromitsu, HIRABAYASHI, Jun-ichi, NOGAMI, Kenji, and SUDO, Yasuaki more...
- Subjects
火山防災情報 ,Volcano monitoring ,火山観測手法 ,Information processing ,情報伝達 ,自動データ処理 ,Volcanic information - Abstract
ワークショップの開催、実践的な教育・普及活動に取り組み、火山防災情報の質の向上にかかわる問題点の整理がかなり進んだ。また、火山活動の評価手法を目指して、薩南諸島の火山において地磁気の連続観測、近年開発されたDOASによる二酸化硫黄の放出率の測定等を行い、また、過去30年間の桜島の火山灰中の揮発成分の分析を行い、他の観測調査データ等と比較することによって、これらの観測・分析手法が火山活動評価や噴火機構研究の有効なツールとなりうることを確認した。さらに、複数の火山の火山性地震を自動分類し、その結果を必要に応じて携帯電話やE-mailで関係者に通報するシステムを開発し、試験運用を開始した。, This paper is a preliminary report that describes the outline of targets and present results of our research project. Problems on volcanic information and education for mitigation of volcanic hazards fairly became clear by a workshop and educational activity. Present results on new tools applied for volcano monitoring at active volcanoes in southern Kyushu are described; geomagnetic observation, remote sensing for volcanic gases, and so on. Basic concept of a system of information processing on seismic data is described. more...
- Published
- 2004
27. 火山防災のための教育普及に関する実践的研究 -エコミュージアムのコンセプトを適用した事例について
- Author
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FUKUSHIMA, Daisuke and ISHIHARA, Kazuhiro
- Subjects
教育 ,education ,火山防災 ,エコミュージアム ,普及 ,ecomuseum ,volcanic disaster prevention ,dissemination - Abstract
地域全体を博物館と考え現地で解説するというエコミュージアムのコンセプトは,その地域の自然や災害の特色を伝えることができる。このコンセプトを桜島で適用し,その有効性を検証した結果,防災を前面に出した教育普及よりも,身近な自然や文化と災害との関連を伝える方が学習効果が高いことが分かった。地域に根ざし,地域の特色を生かした生涯学習の場を提供するエコミュージアムは,防災のための教育普及に有効な方法である。, An ecomuseum is defined as an area where the natural surroundings are theexhibits and the purpose is to inform people about their environment. However, thepurpose of this study is to educate people about local disasters. Therefore, we haveconducted practical research on Mt. Sakurajima to verify whether the concept of anecomuseum can be applied to the dissemination for disaster prevention. It is importantto emphasize the opportunity to enjoy the natural environment and culture of Mt.Sakurajima, and to show how this relates to volcanic disasters. In this way, the conceptof an ecomuseum is an effective way of educating people on disaster prevention. more...
- Published
- 2004
28. Absolute Gravity Measurements at Sakurajima Volcano During the Period 1998-2002
- Author
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YAMAMOTO, Keigo, OKUBO, Shuhei, FURUYA, Masato, ARAYA, Akito, MATSUMOTO, Shigeo, TAKAYAMA, Tetsuro, and ISHIHARA, Kazuhiro
- Subjects
ground deformation ,桜島火山 ,絶対重力測定 ,地盤変動 ,噴火活動 ,eruptive activity ,absolute gravity measurements ,Sakurajima volcano - Abstract
桜島火山では,1975年以降,活発な山頂噴火活動に伴って重力の増加傾向が観測されてきた。桜島の重力場の時空変動を高精度にかつ絶対値で解明する事を目的とし,従来から用いてきたラコスト重力計に加え,1998年よりFG5絶対重力計を用いた絶対重力測定を開始した。2002年までの測定の結果,従来観測されてきた重力の増加傾向が,近年ほぼ停止している事が明らかとなった。近年の山頂噴火活動静穏化を反映した現象であると考えられる。, In Sakurajima volcano, Southern Kyushu, Japan, the remarkable gravity increase has been observed in thecentral region of the volcano during the period of active stage with continuous summit eruptions since 1975. Toclarify both special and time changes of gravity field accurately and in the absolute sense, we began the FG5absolute gravity measurements combined with those using LaCoste gravimeters in 1998. As the result of theevaluation of observed gravity changes during the period from 1998 to 2002, it is found that the gravity increaseobserved since 1975 stops during almost all of our observation periods. This phenomenon seems to relate to thedecreased activities of summit eruptions in recent years. more...
- Published
- 2003
29. Correlation of Lavas on Drilled Cores from the Sakurajima Volcano, Inferred from Paleomagnetic and Chemical Features
- Author
-
MIKI, Daisuke, UTO, Kozo, SUDO, Masafumi, and ISHIHARA, Kazuhiro
- Subjects
全岩化学組成 ,桜島火山 ,古地磁気学 ,volcanic history ,chemical composition ,paleomagnetism ,drilled core ,火山活動史 ,ボーリングコア ,Sakurajima volcano - Abstract
桜島火山の観測井ボーリングコア中の溶岩や地表に露出する溶岩について蛍光X線法による主要元素組成分析を行った。これらの溶岩の主要元素組成は,コアの全長にわたって一様であったハルタ山観測井を除いて, コア内での古地磁気学的な区分および対比された地表溶岩ごとによい一致を示す。桜島北東に位置する新島観測井下部の溶岩の化学組成は,地表に噴出した安永溶岩よりは安永諸島溶岩に近い。また,リンやチタンの含量の多寡には噴出時期によって一定の傾向が見られる。, Whole-rock chemical composition of lavas are measured on drilled cores from observation wellsin Sakurajima volcano. Chemical features are consistent with previously obtained paleomagneticcorrelation, except the Harutayama observation well, at which a uniform chemical composition was found.A lava sample from bottom part of the Shinjima observation well showed similar chemical composition tothe An'ei Islands lava. Studied lavas are possible to be divided into four eruptive stages by their P2O5 andTiO2 contents and ages. more...
- Published
- 2003
30. Mechanics of Explosive Eruption at Sakurajima Volcano-Relation between Source Process of Explosion Earthquake and Air-shock
- Author
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TAMEGURI, Takeshi, IGUCHI, Masato, and ISHIHARA, Kazuhiro
- Subjects
爆発的噴火 ,桜島火山 ,explosive eruption ,air-shock ,gas pocket ,爆発地震 ,ガス溜まり ,explosion earthquake ,空気振動 ,Sakurajima volcano - Abstract
桜島火山における爆発的噴火に伴う爆発地震の震源過程と空気振動データから, 爆発的噴火の発生メカニズムについて考察を行った。爆発地震の震源過程解析から, 爆発地震発生の0.9-1.1秒後に火口底下0.25-0.5kmにおいて等方膨張, その後, 水平収縮が発生しているという結果が得られた。また, 空気振動の発振時および振幅と爆発地震の震源過程の比較から, 空気振動は火口直下浅部における等方膨張によって励起されていることが明らかになった。等方膨張は火口直下浅部に蓄積されたガス溜まりの増圧によって, 水平収縮はガス溜まりの破裂の後, ガス放出による火口付近の減圧によって生じていると考えられる。, Source process of explosion earthquakes that accompany explosive eruptions at Sakurajima volcano, was investigated to clarify mechanical process of explosive eruption. The results of source process showed that the explosion earthquake was initiated by an isotropic expansion and a cylindrical contraction at a depth of 2km beneath the crater bottom. A shallow isotropic expansion at depths of 0.25-0.5km beneath the crater bottom was followed by the explosion earthquake after 0.9-1.1s. The origin time of shallow isotropic expansion coincided with generation of air-shock at the crater bottom and seismic moments of shallow expansion source were correlated with the amplitudes of air-shock. It is inferred that the isotropic expansion is caused by instantaneous pressure increase in the gas pocket formed at the uppermost part of the volcanic conduit, which generates air-shock. more...
- Published
- 2002
31. Monitoring geomagnetic total intensity using satellite telecommunication at Kuchierabujima volcano
- Author
-
KANDA, Wataru, TANAKA, Yoshikazu, UTSUGI, Mitsuru, IGUCHI, Masato, and ISHIHARA, Kazuhiro
- Subjects
火山観測 ,地磁気全磁力 ,Kuchierabujima ,427.9 ,口永良部島 ,geomagnetic total intensity ,453.5 ,衛星通信 ,熱消磁 ,observation in volcano ,satellite telecommunication ,thermal demagnetization - Abstract
近年水蒸気爆発が繰り返されてきた口永良部島火山の山頂部において、2000年8月より地磁気全磁力観測を行っている。火山性地震の震源域で熱消磁が起こった場合を想定して観測点を選定し、データは、オーブコムという衛星通信を利用して研究室へ転送している。今のところ火山活動に起因すると考えられるような変動は捉えられていないが、通信に関しては100%成功しており、小型・軽量・省電力のオーブコム通信を火口近傍の観測に利用する目処がたった。, Variations of geomagnetic total intensities have been measured since August 2000 around the summit crater of Kuchierabujima volcano where phreatic eruptions were repeatedly occurred. The measurement sites were determined so as to detect the change in total intensity due to thermal demagnetization at hypocentral zone of volcanic earthquakes. The observed data are transferred to the office at Sakurajima through satellite telecommunication service called orbcomm. No volcanomagnetic effect has been observed by now. Data transfer via the orbcomm service has been perfectly working, which suggests that this concise system with a small lightweight body and low power consumption could be utilized for observations close to the active crater. more...
- Published
- 2001
32. K-Ar dating of volcanic rocks along the Aira caldera rim: part 2-volcanic history of western and northwestern area of caldera and Sakurajima volcano
- Author
-
SUDO, Masafumi, UTO, Kozo, MIKI, Daisuke, and ISHIHARA, Kazuhiro
- Subjects
K-Ar年代測定 ,K-Ar dating ,姶良カルデラ ,magma chamber ,桜島火山 ,volcanic history ,マグマ溜まり ,453.8 ,Aira caldera ,火山活動史 ,Sakurajima volcano - Abstract
姶良カルデラ西縁部の吉野台, 北西縁部の青敷玄武岩, 及び桜島火山に分布する火山岩のK-Ar年代測定を行った。その結果, 吉野台のカルデラ壁は0.35Ma以降に形成されたことが明らかになった。また青敷玄武岩の年代値は0.08±0.02Maであり, 姶良火砕噴火の数万年前の玄武岩質マグマ活動の存在を示唆する。桜島火山のボーリングコア試料の再測定結果は最近1万年以内の年代値を示し, 既存の値と矛盾しない。, Volcanic history of Aira caldera was discussed by K-Ar dating of volcanic rocks from western Yoshino-dai area, Aoshiki basalt at northwestern Kamo area and those from Sakurajima volcano. The result implies that the caldera wall at Yoshino-dai area formed at least after 0.35 Ma. The K-Ar age of 0.08 Ma from Aoshiki basalt also implies that the activity of basaltic magmas occurred a few ten thousand years before the Aira pyroclastic eruption. The reanalysis of lava flow from the bottom in the Harutayama onservation well of Sakurajima volcano shows its eruptive age within a ten thousand years, which agrees with the previous result. more...
- Published
- 2001
33. K-Ar dating of volcanic rocks along the Aira caldera rim - Volcanic history before explosive Aira pyroclastic eruption
- Author
-
SUDO, Masafumi, UTO, Kozo, MIKI, Daisuke, ISHIHARA, Kazuhiro, and TATSUMI, Yoshiyuki
- Subjects
K-Ar年代測定 ,K-Ar dating ,姶良カルデラ ,爆発的噴火 ,magma chamber ,explosive eruption ,volcanic history ,マグマ溜まり ,453.8 ,Aira caldera ,火山活動史 - Abstract
姶良カルデラにおいて2万5千年前に起こった, 爆発的な姶良火砕噴火に至るまでの火山活動をK‐Ar年代測定法により調べた。姶良カルデラ縁に分布する火山岩32試料のK-Ar年代値によると, (1)3‐lMaにカルデラ南北縁で安山岩質, (2)1‐0.4Maに北西縁で玄武岩‐流紋岩質, (3)0.4‐0.1Maに南西縁で玄武岩‐流紋岩質, (4)0.1‐0.025Maに北縁で安山岩質, 及び南北線でほぼ同時期に流紋岩質の活動が起こった。姶良カルデラ直下において現在存在が推定される流紋岩質マグマ溜まりは(4)の時期には既に存在していたのかもしれない。キーワード:姶良カルデラ, K。Ar年代測定, 火山活動史, 爆発的噴火, マグマ溜まり, A volcanic history before the explosive Aira pyroclastic eruption at 24.5 ka was investigated by K-Ar dating method. Thirtytwo K-Ar ages from volcanic rocks along Aira caldera show the following time-space distribution; (1) 3 to 1 Ma: andesitic lava flows (northern and southern areas of Aira caldera), (2) 1 to 0.4 Ma:basaltic to rhyolitic lava flows (northern and western area), (3) 0.4 to 0.1 Ma: basaltic to rhyolitic lava flows(southern and western area), (4) 0.1 to 0.025 Ma: andesitic lava flows (northern area) and rhyolitic lava flows having very similar ages both in northern and southern areas.The rhyolitic lava flows in the period of (4) imply that the rhyolitic magma chamber has been formed during the period. more...
- Published
- 2000
34. Self-Potential and Hydrothermal System in Sakurajima Volcano (2)
- Author
-
HASHIMOTO, Takeshi, TANAKA, Yoshikazu, NISHIDA, Yasunori, MOGI, Tohru, YAMAMOTO, Keigo, KANDA, Wataru, HIRABAYASHI, Jun'ich, and ISHIHARA, Kazuhiro
- Subjects
Sakurajima ,self-potential ,hydrothermal system ,426.3 ,対流系 ,streaming potential ,流動電位 ,桜島 ,volcano ,熱水系 ,453.8 ,自然電位 ,火山 ,convection ,455.1 - Abstract
桜島火山東部において自然電位分布を測定した。海水面を等電位とみなして過去に得られた電位分布と接続することにより, 島を東西に横断する測線で約3分の2の長さにわたって電位分布を得ることができた。桜島の山頂部に向かって電位が高くなる傾向が認められることから, 島の中央部地下にその上昇部をもつ全島規模の熱水対流系が存在する可能性が示された。, We conducted a self-potential survey in the eastern part of Sakurajima volcano. We combined the SP data with those of previous studies by assuming the equi-potential of the sea water. Consequently, we have obtained a SP profile across the Sakurajima from west to east, though the active summit area still remains to be measured. After the linear topographic correction, we found that the SP increases toward the summit of the volcano. It suggests a large hydrothermal convention cell of a whole-island scale with its upwelling part under the central vent. more...
- Published
- 1999
35. 平成10年度防災研究所公開講座'災害の予知と予測II'-その現状と将来の展望-パネルディスカッション-予知・予測の現状と将来について
- Author
-
FURUSAWA, Yutaka, UEDA, Hiromasa, NAKAGAWA, Hajime, KAWATA, Yoshiaki, ISHIHARA, Kazuhiro, and SUZUKI, Yoshiyuki
- Subjects
519.9 ,453.38 - Published
- 1999
36. K-Ar dating and paleomagetic measurements on drilled cores from the Sakurajima volcano - Preliminary attempts to reveal the history of the volcanic activity
- Author
-
UTO, Kozo, MIKI, Daisuke, UCHIUMI, Shigeru, and ISHIHARA, Kazuhiro
- Subjects
K-Ar年代測定 ,K-Ar dating ,427.9 ,桜島火山 ,古地磁気学 ,volcanic history ,paleomagnetism ,453.8 ,火山活動史 ,Sakurajima volcano - Abstract
桜島火山の黒神, ハルタ山両観測井掘削コアについてK-Ar年代測定と古地磁気測定を行ない, 噴出年代推定を試みた。黒神観測井の3枚の溶岩流は全てAD764年長崎鼻溶岩とほぼ同時期に噴出したと考えられ, その下に姶良カルデラ形成前後の火山岩類が分布する。ハルタ山観測井のコアの4枚の溶岩は, 5千年より最近の複数回の噴火により流出した。両手法の複合的組み合わせにより, 数万年以内の火山噴出物の直接年代推定がより正確に行えると期待される。, Preliminary K-Ar dating and paleomagnetic measurements were made on drilled cores from two observation wells in Sakurajima volcano to obtain the chronological information. Three lava flows found in the Kurokami observation well are considered to belong to AD764 Nagasakibana lava flow, and volcanic clasitcs below these lavas could have been erupted immediately before or after the formation of the Aira caldera at ca. 25, 000 years ago.Four lava flows found in the Harutayama observation well would have been erupted successively by the multiple eruptions within recent about 5, 000 years. more...
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- 1999
37. Volcanic activity at Satsuma-Iwojima during 1995-1998
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IGUCHI, Masato, ISHIHARA, Kazuhiro, TAKAYAMA, Tetsuro, TAMEKURI, Takeshi, SHINOHARA, Hiroshi, and SAITO, Eiji
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A-type earthquake ,ground deformation ,地盤変動 ,455.8 ,Satsuma-Iwojima ,噴気活動 ,A型地震 ,453.5 ,薩摩硫黄島 ,B型地震 ,B-type earthquake ,453.8 ,fumarolic activity - Abstract
薩摩硫黄島は, 島の東部にある硫黄岳の山頂火口において活発な噴気活動を続けている.京都大学, 地質調査所, 福岡管区気象台により行なわれている地震観測, GPSの繰り返し測定および火口内の地形, 噴気の調査結果から, 1995年-1998年の薩摩硫黄島の活動は次のようにまとめられる.(1)薩摩硫黄島においても桜島火山と類似した種類の火山性地震A型, B型およびC型(モノクロマティック微動)が発生している.(2)1995年から1998年のA型地震の発生頻度には, 顕著な変化はみられず, 1975年-1978年における発生頻度と比較しても大きな変化はない.また, 正断層型のメカニズムをもつA型地震が火口の西側に震源決定されたが, その震源位置は1975年-1978年における発生位置と同様である.(3)1996年6月8日に発生したM=2.9の有感地震は, それ以外のA型地震と比べて規模が大きい.硫黄岳山頂火口近傍の測量基準点は, 1995年6月から1997年4月の間に6cm北東に変位した.また, 火口の南東側周辺に割れ目が形成された.この地震の発生は火口周辺の地盤変動および火口の南東における割れ目の形成と関連があるのかもしれない.(4)B型地震は, 山頂火口直下の浅い場所において発生している.その発生頻度は, 1998年7-8月には1日に15回程度であったが, 10月以降は, 1日150回程度に増加した.B型地震は体積膨張型のメカニズムをもち, 火山ガスの膨張と関連している可能性が高い., Fumarolic activity has continued at the summit crater of Satsuma-Iwojima volcano located south off Kyushu, Japan. Sakurajima Volcanological Observatory (SVO), DPRI, Kyoto University has conducted seismic observation at a permanent station 1.5 km west of the summit crater since June 1995. Fukuoka Meteorological Observatory installed 4 stations at the volcano since September 1997. Geological Survey of Japan has repeated visual, geochemical, topographical survey at the crater. SVO and GSJ have cooperated in GPS measurement since June 1995. Volcanic activity of Satsuma-Iwojima is summarized as follows; (1)Volcanic earthquakes are classified into A-type (high frequency), B-type (low frequency) and C-type (monochromatic tremor). (2) A-type earthquakes occurred at the west of the summit crater at a depth of 1km. The focal mechanism of the A-type earthquakes is normal fault type. (3) B-type earthquakes are located at very shallow depth beneath the summit crater. B-type earthquakes are generated by expansive volumetric source, maybe expansion of gas pocket. (4) The seismicity of A-type earthquakes during 1995-1998 is the same as that in 1975-1978, except the earthquakes at 21:06 on June 8, 1996. (5) A crack with length of lOOm was formed southeast of the summit crater before October 1996. The benchmark near the crack moved eastward by 6 cm during the period from June 1995 to April 1997. The earthquakes on June 8, 1996 may be related with topographic change and ground deformation around the crater. more...
- Published
- 1999
38. Evaluation of the Recent Activity at Guntur Volcano, West Java, Indonesia
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IGUCHI, Masato, ISHIHARA, Kazuhiro, ETO, Tsuneo, YAMAMOTO, Keigo, SUTAWIDJAJA, Igan S., SUANTIKA, Gede, SUGANDA, Ony K., and HENDRASTO, Muhamad
- Subjects
ground deformation ,発震機構 ,地盤変動 ,focal mechanism ,455.8 ,volcanic earthquake ,Guntur ,453.5 ,Guntur火山 ,hypocenter ,453.8 ,火山性地震活動 ,震源分布 - Abstract
インドネシア・ジャワ島西部にあるGuntur火山では, 最近約150年間噴火が発生していないが, 火山性地震の活動は活発であり, 山頂付近と西部のKamojangカルデラ付近に火山性地震が分布する。Kamojangカルデラ付近の地震は, 北東から南西方向に直線状に分布し, 震源の深さは5-10kmである。発震機構は南北伸張, 東西圧縮となる横ずれ型のメカニズム解となる。一方, 山頂付近の地震は, 火山列に沿って北西-南東方向に分布し, 震源の深さは5km以下と浅い。マグニチュードも1以下と小さい。正断層または逆断層型の発震機構をもつ。1997年5月から山頂直下の深さ2-5kmにおいて火山性地震の発生頻度が増加したが, 5月29日, 10月7, 8日のように発生頻度が高いときはすべて逆断層型となる。一方, 山頂の南2kmに設置された傾斜計により, 地震活動の活発化と同期して山頂方向の地盤の隆起が観測された。山頂方向の地盤の隆起現象は, 南東山麓の水準測量によっても確認されている。これらのことから, 1997年5月以降の地震活動は, 山頂部の火山列に沿う断層において発生している。また, 火口直下で圧力の増加があり, 圧力源の直上の地盤が押し上げられ, その結果として逆断層型の地震が発生したと解釈される。1997年5月-11月の地震活動度を1991年以降の地震活動の推移の中で評価してみた。地震活動の活発化は1992年5月-7月, 1993年5月-8月にもみられる。この3期間の活動の増加に共通してみられることは, 主として山頂直下において地震が多発したこと, また, Kamojangカルデラ周辺で活動が活発化したことである。1997年5月-11月における山頂直下での地震の放出エネルギーは1992年と1993年の活動と同程度であり, 今回の活動はGuntur火山において, 1-数年の間隔で繰り返される10^15-10^16ergの規模のエネルギーの放出を伴う地震活動の活発化の1つであるといえる。, Guntur is a volcano-complex, West Java, Indonesia and is located 35km SE of Bandung. Explosive eruptions and lava flows were repeated at Guntur Crater since 17th century, however, no eruption has occurred for 150 years after the 1843 eruption. Volcanological Survey of Indonesia began to monitor the volcano by a seismometer at a station 0.8 km east of the summit crater. In 1994, 3 seismic stations were added to determine hypocenters in collaboration with DPRI, Kyoto University. Volcanic earthquakes are located in the summit area (aligned from SE to NW along the volcano line from Guntur to G. Masigit) and Kamojang area west of the summit. In Kamojang area, earthquakes are distributed from Gandapura (NE) to Darajat caldera (SW) at depth of 5-10 kim, with the strike slip mechanism, similarly to tectonic earthquakes in inland area. In contrast, volcanic earthquakes beneath the summit are shallower ( more...
- Published
- 1998
39. Self-Potential and Hydrothermal System in the Western Part of Sakurajima Volcano
- Author
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HASHIMOTO, Takeshi, TANAKA, Yoshikazu, MOGI, Tohru, NISHIDA, Yasunori, OHBA, Shigeyuki, YAMAMOTO, Keigo, and ISHIHARA, Kazuhiro
- Subjects
桜島 ,Sakurajima ,volcano ,熱水系 ,electric sounding ,self-potential ,hydrothermal system ,453.8 ,電気探査 ,自然電位 ,火山 ,455.1 - Abstract
桜島火山西部の大正噴火割れ目のやや北側に帯状の自然電位異常が検出された。一方, この異常を横切る測線での直流電気探査によって, 爆裂火口である引ノ平の地下に高抵抗体が, 高電位部の地下には低比抵抗体が存在することが明らかになった。これらの結果から, この高電位異常は地下における熱水対流の上昇部に対応しており熱水の流動は溶岩の固結した火口ではなくそれに隣接した破砕域で卓越していることが推察される。, A banded self-potential (SP) anomaly was found in the westem part of Sakurajima volcano, southwestem Japan.This positive SP anomaly lies along the fissure of 1914 eruption and probably corresponds to the upflow part of subsurface hydrothermal convection. A DC electric sounding conducted along the survey line across the banded anomaly revealed that a conductive part exists 50-1OOm below the positive SP anomaly. These results suggest that the hydrothermal fluid flow is more prominent in the fractured zone adjacent to a vent than in the vent itself chokedwith the solidified lava. more...
- Published
- 1998
40. Trend of gravity change in and around Sakurajima volcano
- Author
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YAMAMOTO, Keigo, TAKAYAMA, Tetsuro, ISHIHARA, Kazuhiro, OSHIMA, Hiromitsu, MAEKAWA, Tokumitsu, UEKI, Sadato, SAWADA, Munehisa, and OIKAWA, Jun
- Subjects
桜島 ,Sakurajima ,ground deformation ,地盤変動 ,455.8 ,精密重力測定 ,噴火活動 ,eruptive activity ,precise gravity measurement ,448.2 ,453.8 - Abstract
1997年4月に桜島および姶良カルデラ周辺で, 9回目の精密重力測定を実施した。姶良カルデラ周辺の測定点における重力変化傾向は, 定性的には地盤変動から期待される重力変化に調和的であった。桜島中央部を中心とした1975年以降1992年まで続いた重力増加傾向は, 前回(1992年)から今回の測定の問, それ以前に比べて鈍った。近年の山頂噴火活動の静穏化を反映しているのではないだろうか。, The 9th precise gravity measurement was conducted in and around Sakurajima in Apr. 1997. The trend of gravity changes around Aira caldera is in harmony with that expected from the ground deformation.Successive gravity increase observed around the center of Sakurajima since 1975 seems to slow down between the last (1992) and the present measurements. It may reflect the low activity of summit eruption of Sakurajima since 1993. more...
- Published
- 1998
41. Hypocentral Distribution and Focal Mechanism of Volcanic Earthquakes around Guntur Volcano, West Jawa, Indonesia
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SUANTIKA, Gede, SUGANDA, Ony Kurnia, IGUCHI, Masato, and ISHIHARA, Kazuhiro
- Subjects
グントール火山 ,発震機構 ,focal mechanism ,volcanic earthquake ,453.5 ,Guntur volcano ,火山性地震 ,hypocenter distribution ,震源分布 - Abstract
京都大学防災研究所火山活動研究センターはインドネシア火山調査所と共同して, ジャワ島西部にあるグントール火山に4観測点からなる定常地震観測網を設置し, 1994年11月から観測を続けている。また, 1995年12月から1996年2月, 1996年9月から12月にかけて臨時地震観測を行った。その結果, 次のことが明らかになった。(1)火山性地震は, 山頂の火口直下の海面下深さ0-5kmに円筒状に分布する。また, 北西部のガンダプラカルデラ, 西部のカモジャンカルデラ周辺, 南部のプツリ山直下にも分布している。特に, 臨時多点観測による精密震源決定では, カモジャンカルデラ周辺の地震は深さ10kmまでに地表に現れた断層の延長線上に直線的に分布することが明らかになった。(2)カモジャンカルデラの周辺の地震の多くは, 節線が北東-南西, 南東-北西を向く横ずれ断層のメカニズムをもつ。一方, 山頂火口周辺では正断層および逆断層となる解が得られたが, 系統的なメカニズム解は得られなかった。(3)カモジャンカルデラ周辺の地震は, この地域に特徴的な北東-南西方向の断層の右横ずれ運動によって発生したものと考えられる。一方, 山頂火口周辺の地震は, 過去の噴火によって形成された火道周辺の岩石の様々な方向への微少破壊によるものと思われる。火口周辺の地震のマグニチュードの上限が0, 7であることは, このことと調和的である。, Guntur Volcano is an andesitic volcano, located in West Java, Indonesia. A seismic network composed of 4 stations has been installed at Guntur Volcano since October, 1994, in the collaborative study between Sakurajima Volcanological Observatory, DPRI, Kyoto University and Volcanological Survey of Indonesia, DGGMR, Indonesia. Temporary seismic observations were conducted in December 1995-February 1996 and September - December 1996.Locations of hypocenters were calculated assuming a homogeneous half space of Vp=2.76 km/s. The epicenters seem to be vertically concentrated beneath Guntur summit at depths of 0-5 kim, around Kamojang caldera (west of the summit), Gandapura (northwest) and G. Putri (south). The precise determination of hypocenter by temporary observation revealed that the hypocenters are aligned along faults at depth of 5-10 km.Focal mechanisms of 23 volcanic earthquakes were determined. Mechanisms of most of the events around Kamojang Caldera are generally strike-slip fault with the fault plane direction of NE-SW and NW-SE. Considering the hypocentral distribution and surface geological structure, it is inferred that the earthquakes originate by the slip of the fault to NE and SW. Mechanisms of four events were determined. The mechanisms are normal fault and reverse type. Composite source mechanism in the area did not show consistent character. This suggests that the rocks in hypocentral zones beneath the crater are fractured more in the many directions maybe due to the previous volcanic activities.The smaller magnitude ( more...
- Published
- 1997
42. Prevention and Mitigation of Aircraft Accidents Caused by Volcanic Eruption
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ONODERA, Saburo, IGUCHI, Masato, and ISHIHARA, Kazuhiro
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Aircraft ,Volcanic Eruption ,Flight Operations ,噴火 ,桜島 ,火山灰 ,Sakurajima Volcano ,Volcanic Activity ,453.8 ,火山活動 ,航空機 ,Volcanic Ash ,538.88 ,運航 - Abstract
京都大学と日本航空は火山と空港・航空路とが互いに隣接しあい, 火山灰回避の為の時間的余裕が少ない鹿児島空港から桜島周辺地域において, 火山活動に起因する航空機災害防止を図る為, 桜島火山の活動の事前予測, 爆発的噴火の検出, 火山灰拡散の予測, 及びそれらの情報の鹿児島空港への迅速な情報伝達について共同で研究した。その結果, 航空機災害防止に有効なシステムの開発に成功した。, In order to mitigate volcanic ash hazards to aircraft, Kyoto University and Japan Airlines have developed systems at Sairurajima Volcano and in the Kagoshima Airport region by methods of (1)predicting volcanic activities, (2)detecting volcanic eruptions, and (3) predicting volcanic ash trajectory and transport.The results were successful. This suggests one comprehensive system for the mitigation of volcanic ash hazards in volcano regions that have air routes located in the proximity. more...
- Published
- 1997
43. Magma Transport at Mt. Unzen Associated with the 1990-1995 Activity Inferred from Leveling Data
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HENDRASTO, Muhamad, ETO, Tsuneo, KIMATA, Fumiaki, MATSUSHIMA, Takeshi, and ISHIHARA, Kazuhiro
- Subjects
水準測量 ,lava dome ,雲仙火山 ,Mt. Unzen ,leveling ,圧力源 ,magma supply ,溶岩ドーム ,453.8 ,マグマ供給率 ,pressure source - Abstract
1990年11月に198年ぶりに噴火活動を開始した雲仙普賢岳は、1991年5月20目からデイサイト質溶岩を噴出し、1995年始めまで、溶岩噴出と火砕流発生を繰り返した。国立大学総合研究班および国土地理院は、雲仙普賢岳の北山麓から山頂へ向かう路線、および島原半島西岸沿いの路線に沿って水準測量を繰り返してきた。また、GPS観測も繰り返された。その結果、島原半島西部の地盤は溶岩流出まで隆起・膨張し、溶岩流出開始後沈降・収縮に転じたことがわかった。これまでの研究によって、普賢岳山頂の直下から西に向かって次第に深さを増す、3つの圧力源、A、BおよびCを仮定すれば雲仙岳周辺の地盤の変動が説明できることが示された。本研究では、水準測量データの測定誤差を考慮した上で、点力源モデルを適用して、3つの圧力源の位置、およびそれぞれの圧力源の強度の時間的変化を再計算した。その上で、溶岩噴出率および地震活動と圧力源の強度の関係、また、地盤の変形体積と溶岩噴出率をもとに地下深部からのマグマ供給率を推定した。[1]普賢岳火口の地下1.4kmに力源A、普賢岳の西方約3km、深さ4.1kmに力源B、および普賢岳西方約5km、深さ6.8kmに力源Cの存在が推定された。各力源は島原半島西方の橘湾から普賢岳に伸びる地震帯の直下に位置する。[2]溶岩噴出開始以降、普賢岳直下の力源Aの強度の変化は、溶岩噴出率と普賢岳の地震活動の増減と対応している。[3]力源Bの強度の変化は溶岩噴出率の2度の増大に対応している。一方、力源Cの強度は溶岩流出開始まで増大し、その後は時間とともに減少している。[4]以上の結果より、マグマが力源Cから、力源Bおよび力源Aを経由して輸送され、普賢岳山頂から噴出したことが推定される。地盤の変動体積の変化が力源でのマグマ蓄積量の増減に等しいと仮定して、地下深部から力源Cへのマグマ供給率を推定した。マグマ供給率は、溶岩噴出開始の約半年前から急増し、1991年終わりにヒ。一クに達し、それ以後減少して、1995年始めには停止した。1990年から1995年までのマグマ供給量は0.17km^3と推定される。, The recent activity of Mt. Unzen (Fugendake) was preceded by an earthquake swarm beneath the Tachibana Bay, west of the Shimabara Peninsula, in November 1989 and the subsequent migration of seismic activity toward Mt. Unzen.On November 17, 1990, phreatic eruption started at the summit, then a dacite lava dome appeared at the summit crater on May 20, 1991. Subsequent discharge of lava and intermittent pyroclastic flows have continued until early 1995. The total volume of discharged lava was 0.2 km^3.Universities and the Geographical Survey Institute had repeated leveling survey along the western coast of the peninsula, and the other route from the northern flank to the summit, and found out significant deflation of the ground centered a few kilometer west of the summit, which was also clarified by GPS survey. The magma supply system composed of three chambers, and an inclined magma pathway along seismic zone were proposed by previous studies.Applying the Point-Source Model (Mogi's Model), the location of three pressure sources and their intensity change with time were re-examined including the evaluation of measurement error of leveling data, and the relationship between the intensity changes at pressure sources and volcanic activity.(1) The near surface source A is located at a depth of 1.4 km beneath the summit, and the source B is 4.1 km deep, 3 km west of the summit. And the deepest one C is located 6.8 km deep, west of the summit. These sources are aligned just beneath the inclined seismic zone.(2) The intensity change at A-source seems to be related to the discharge rate of lava and seismic activity at the summit.(3) The intensity change at B-source has two peaks corresponding to the two epochs of discharge of lava and increased prior to the onset of discharge of lava. The intensity of C source increased until the lava dome appeared, and then gradually decreased.(4) These results suggest magma was transported from C-source through B- and A-sources to the summit. Assuming the deformation volume of the ground surface due to pressure sources is equal to the volume change of magma at each source, the supply rate of magma from deeper portion to C-source was estimated using the data on discharge lava. The supply rate of magma increased rapidly after the phreatic eruption in November 1990, and reached its peak in the end of 1991, then decayed. In early 1995, magma supply stopped.The total volume of magma supplied since 1990 is estimated to be 0.17 km^3 more...
- Published
- 1997
44. Increase in Seismic Activity in 1996 at Kuchierabujima Volcano
- Author
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YAMAMOTO, Keigo, IGUCHI, Masato, TAKAYAMA, Tetsuro, and ISHIHARA, Kazuhiro
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focal mechanism ,口永良部島 ,volcanic earthquake ,Kuchierabujima volcano ,453.5 ,火山性地震 ,hypocentral distribution ,震源分布 ,発露機構 - Abstract
口永良部島火山に発生する火山性地震は, P波, S波の明瞭なA型, 高周波成分の卓越するHF型, 高周波成分と低周波成分の混在するHybrid型, 低周波成分の卓越するLF型および単一の周波数にスペクトルのピークを持つMonochromatic型に分類される。1995年以前は, 1ヶ月に10個以下のHF型地震が観測されていたが, 1996年1月初めの比較的規模の大きいA型地震とLF型地震の発生以後, HF型の発生頻度が高くなっただけでなく, 低周波成分の含まれるHybrid型, LF型およびMonochromatic型が発生するようになった。1996年5月から6月に, 西側山腹に4点, 山麓に6点地震計を設置し, 臨時地震観測を行った。島内における砕石発破を利用してP波速度構造を求めた。Vp=3.3㎞/sの半無限均質構造を仮定して震源決定を行ったところ, A型地震は口永良部島北東部に, その他の種類の地震は, 新岳の火口直下海抜Om付近に集中していることがわかった。LF型およびMonochromatic型の初動は, 全観測点において引きであり, 4象限型の発震機構で説明するのは困難である。, Volcanic earthquakes at Kuchierabujima volcano are classified into 5 types; A-type: tectonic-like earthquake with clear P- and S-phases, HF-type: dominated by high frequency, Hybrid-type: mixed with high and low components, LF-type: dominated by lower frequency, and Monochromatic event. Less than 10 per month HF-type events were observed before 1995. After occurrence of A-type earthquakes and LF events in early January 1996, the number of HF events suddenly increased and Hybrid and LF with lower frequency content and Monochromatic events frequently appeared. Temporary seismic observation was conducted in May and June 1996, installing 6 seismic stations around the summit crater and a small network with 4 seismometers on the western flank. Assuming Vp = 3.3 kim/s estimated from artificial explosions, locations of the earthquakes were determined. Two A-type earthquakes were located northeast off the volcano and the other types were concentrated beneath the summit crater at depth of sea level. P-wave first motions of LF and Monochromatic event were dilatation at all the station. The mechanism of the events may not be double-couple. more...
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- 1997
45. SEISMIC ACTIVITY AT GUNTUR VOLCANO, WEST JAVA, INDONESIA
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IGUCHI, Masato, ISHIHARA, Kazuhiro, TAKAYAMA, Tetsuro, SUANTIKA, Gede, TJETJEP, Wimpy S., SUKHYAR, Raden, SUTAWIDJAJA, Igan S., and SUGANDA, Ony K.
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455.8 - Abstract
Guntur volcano is an andesitic volcano, located in West Jawa, Indonesia. The last eruption occurred in 1843 and no eruptions have occurred since then, however, seismic activity has been active. A seismic network composed of 4 stations has been operated since October, 1994, in the collaborative study between Sakurajima Volcanological Observatory, DPRI, Kyoto University and Volcanological Survey of Indonesia, DGGMR, Indonesia. Seismic signals are transmitted to Guntur Volcano Observatory and recorded in data loggers in which timing system is calibrated by GPS. Locations of hypocenters are calculated assuming a homogeneous half space of Vp = 2.76 km/s determined previously. Hypocenters are distributed at depth of 0 to 4 km beneath sea level around Guntur crater, 0 to 2 km beneath west of Guntur crater and at depth of < 10 km around Kamojang caldera. The hypocentral locations are calibrated by adding 7 stations temporarily during December 1995 to February 1996. The result of calibration shows Vp value of 2.76 km/s is acceptable as velocity of P-wave in determination of hypocenters by using 4 permanent stations and assuming homogeneous half space. The hypocenters seem to be distributed vertically beneath Guntur crater and aligned along faults near Kamojang caldera. Magnitude of earthquakes in the cylindrical zone beneath Guntur crater is < 0.7 and that out of the zone is < 3. This suggests the rock beneath the crater was highly fractured by previous eruptions. more...
- Published
- 1996
46. Microgravity survey around active volcanoes in Hokkaido, Japan
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MAEKAWA, Tokumitsu, MIYAMACHI, Hiroki, OSHIMA, Hiromitsu, and ISHIHARA, Kazuhiro
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450.12 - Published
- 1996
47. VOLCANIC EARTHQUAKES AND TREMORS AT SEMERU VOLCANO, INDONESIA, AND THE COMPARISON WITH THOSE AT SAKURAJIMA AND SUWANOSEJIMA VOLCANOES
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ISHIHARA, Kazuhiro, IGUCHI, Masato, SUANTIKA, Gede, and SUKHYAR, Raden
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427.8 - Abstract
Semeru volcano, an andesitic stratovolcano in East Java, Indonesia has erupted inter-mittently for more than 50 years. On February 3, 1994, the volcano erupted violently accompanied with remarkable pyroclastic flows. Seismic activity prior to the eruption was characterized by occurrence of deep volcanic earthquakes, and successive increase in shallow earthquakes and tremors continuing for 9 days until the eruption. Such a sequence of the seismic activity has been often observed at Sakurajima. Volcanic earthquakes and tremors observed at the volcano are quite similar to those recorded at Sakurajima and Suwanosejima volcanoes; those are A-type earthquakes, B-type earthquakes, explosion-earthquakes, harmonic (C-type) tremors and non-harmonic tremors. Spectral analysis for these events at the three volcanoes were done. The peak frequencies of them at Semeru and Sakurajima are almost same, but lower than those at Suwanosejima. This result suggests that Semeru has a shallow magma conduit of similar size with that of Sakurajima. It is noteworthy that harmonic tremors at Semeru have a few discrete frequency peaks of integer multiple, and the frequencies change with time, similar to those at the other two volcanoes. more...
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- 1995
48. PRELIMINARY REPORT ON COMPARATIVE STUDY OF ERUPTION MECHANISM OF MERAPI VOLCANO IN INDONESIA WITH JAPANESE VOLCANOES
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KAMO, Kosuke, ISHIHARA, Kazuhiro, IGUCHI, Masato, チェチェップ, ウィンピー S., TJETJEP, Wimpy S., SUBANDRIYO, SUHARNO, RATDOMOPURBO, Antonius, スガンダ, オニー K., and SUGANDA, Ony K.
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453.8 - Abstract
The eruptive activity of Merapi, the precursory phenomena and its magma supply system are summarized based on research made by the Volcanological Survey of Indonesia and are discussed in comparison with those at Mt. Unzen and Sakurajima.Although the output rate of lava and the type of magma at Merapi are much different from those at Mt.Unzen in 1991-1992, the sequence of eruptive activity and precursory phenomena are basically similar with each other: explosive eruptions at the intial stages of activity, pyroclastic flows due to collapse of lava domes, growth of lava domes by repeated domings, precursory seismic activity and remarkable ground deformation of summit area and so on. Magma supply system at Merapi inferred from the hypocentral distribution of volcanic earthquakes are quite similar with that at Sakurajirna: the vertically elongated distribution from the summit to 5 km in depth, a seismicity gap at 2-3 km deep and aseismic zone below 5 km. These suggest the vertical magma conduit of 5 km long from magma reservoirs to the summit and a magma pocket around 2-3 km deep at the both volcanoes. more...
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- 1994
49. CONTINUOUS MAGMA SUPPLY INFERRED FROM DISCHARGE RATE OF MAGMA AND GROUND-DEFORMATION RATE AT MT. UNZEN, JAPAN
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ISHIHARA, Kazuhiro
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455.8 ,453.8 - Abstract
The current eruptive activity at the Fugendake, one of the central cones of Mt. Unzen started on 17 November in 1990, after the 198 years of dormant period.Dacitic lava has been extruded at a rate of 10 5m3/day from one of the summit craters since late-May of 1991.The cumulative volume was 0.12 km3 as of November, 1992.Geodetic survey detected gradual inflation prior to the extrusion of lava and subsequent deflation after the onset of lava extrusion around the western foot of the volcano.Tha analysis of the ground-deformation data suggested that a magma storage is located several kilometers deep, a few kilometers west of the eruption center.Quantitative relationship between integrated deformation volume of the ground surface and the amount of discharged lava suggests continuous supply of magma from a lower-crustal magma reservoir into the shallow storage.The supply rate during th past two years was estimated to be (1-2) x l0 7 m3/year.Some andesitic or dacitic volcanoes which have erupted over a few decades commonly indicate a similar discharge rate of magma (and its supply rate) as the rates at Mt. Unzen, and the estimated supply rate of magma also satisfies the condition of constant magma ascent deduced theoretically by Fedotov.Therefore, the volcanic activity at Mt. Unzen may presumably persist during a few decades. more...
- Published
- 1993
50. COMPARISON OF EARTHQUAKES AND AIR-SHOCKS ACCOMPANIED WITH EXPLOSIVE ERUPTIONS AT SAKURAJIMA AND SUWANOSEJIMA VOLCANOES
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IGUCHI, Masato and ISHIHARA, Kazuhiro
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501.24 ,453.8 - Abstract
Some characteristics of earthquakes and air-shocks are compared among three styles ofexplosive eruption, those are, explosion and successive minor eruption at Sakurajima, and ex-plosion at Suwanosejima. The following results are obtained.1) The maximum amplitudes of vertical component are 3-30 mkine in explosion earthquakesat Sakurajima, less than 13 mkine in eruption earthquakes at Suwanosejima and less than 7mkine in BL-type earthquakes at Sakurajima. The epicentral distances are around 3 km. Theamplitudes of compressional phase of air-shocks are 0.2-5 mb in explosions at Sakurajima, lessthan 2 mb in explosions at Suwanosejima and less than 0.1 mb in successive minor eruptions atSakurajima. The infrasonic microphones are 6 km and 3.3 km apart from the craters at Sakura-jima and Suwanosejima, respectively.2) Comparing the three styles of eruptions in the same amplitude-range of eruption earthquakes(5-7 mkine), the amplitudes of air-shock by explosions at Suwanosejima are larger than those bysuccessive minor eruptions at Sakurajima, but are smaller than those by explosions at Sakuraji-ma. This result suggests that the ratio of seismic energy to infrasonic one changes with theseeruption styles.3) The intensity of the explosions in the active period during 1988-1989 at Mt. Tokachi wasas large as that of the strongest explosions at Suwanosejima in 1989. However, the volume ofpyroclastic materials, the time interval of eruption and the duration of compressional phase ofair-shock at Mt. Tokachi are closer to those at Sakurajima. more...
- Published
- 1990
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