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  • 辻 智大, 岸本 博志, 藤田 浩司, 中村 千怜, 長田 朋大, 木村 一成, 古澤 明, 大西 耕造, 西坂 直樹, 池田 倫治, 太田 岳洋, 福岡 仁至
    火山
    2023年 68 巻 3 号 129-160
    発行日: 2023/09/30
    公開日: 2023/11/02
    ジャーナル フリー
    電子付録

    Kuju volcano, located within Beppu-Shimabara graben central Kyushu, Southwest Japan, has been active in the recent 200,000 years. The 54 ka Handa eruption, as large as VEI 5 or 6 and the largest one of the volcano, released large-scale pyroclastic flow deposits (Handa pfd; Kj-Hd) and a wide-spread tephra (Kj-D ash and Kj-P1 pumice fall deposits) that has been reported at more than 500 km from the source. The stratigraphic relationships among the deposits from the Handa eruption are important for volcanology and disaster prevention, and have been studied in various studies, but there is no consensus on the stratigraphy. In this study, we examined the stratigraphic relationships and the eruption history based on the stratigraphic and petrographic studies around Kuju volcano, as well as on Shikoku and Honshu Islands.

    As the results, the stratigraphic relationships were revealed as follows.

    1) The pumice fall deposit, that has been named Kj-Yu, was previously included in Kj-D ash layers, but is revealed to be a much older ejecta than Kj-D ash, along with the tephras newly named Kj-Tb1 and 2.

    2) The clay-rich layer just below Kj-D was previously considered to be soil, but it contains a large number of volcanic ash particles so that it is defined as Kj-Y ash layer.

    3) Three light brown fine ash layers, newly named Kj-D-U2, 4 and 6, sandwich between the blue grey sandy ash layers i.e. Kj-D-U1, 3, 5 and 7, are revealed to be the co-ignimbrite ash derived from Kj-Hd 1, 2 and 3 pfd, respectively. It suggests that the Kj-Hd1, 2 and 3 pfd are interbedded with Kj-D-U ash layers.

    4) Kj-P1 overlies on Kj-D-U7 ash layer that mantled the reworked deposit of Kj-Hd3.

    5) Kj-P1 is divided into lower and upper units based on the grain-size analysis, petrography, the chemical composition of glass shards and the isopach maps. Kj-S pfd was formed in the same time as the upper unit.

    Based on the results, the eruption history is assumed as follows.

    Pre-Handa eruption: the activity was low and the small-scale explosive eruptions that had released the pumice and volcanic fragments in loam (Kj-Y), followed by a relatively large explosive eruption that had formed Kj-AL.

    Early phase: the eruption started with phreatic eruption, sub-plinian eruption that deposited the lower unit of Kj-D ash. Subsequently, the eruption changed to vulcanian eruptions that ejected Kj-D-U. This eruption continued for a long period time. During the time, three large-scale pyroclastic flow eruptions happened and has formed Kj-Hd1, 2 and 3. Their co-ignimbrite ashes generated from the Kj-Hd pfds were deposited as Kj-D-U2, 4 and 6. Lahar were generated after Kj-Hd2 and 3 deposition. This phase was terminated by the deposition of Kj-D-U7 ash.

    Late phase: the plinian plumes occurred twice and deposited lower and upper lalyers of Kj-P1. The second one is the largest plinian eruption in the whole volcano history, with a large umbrella plume producing a wide-spread tephra at more than 500 km from the source and an intraplinian pyroclastic flow (Kj-S).

  • *辻 智大, 岸本 博志, 藤田 浩司, 三浦 大助, 池田 倫治, 西坂 直樹, 大西 耕造
    日本火山学会講演予稿集
    2017年 2017 巻 B1-11
    発行日: 2017年
    公開日: 2018/02/01
    会議録・要旨集 フリー
  • 山口 頼央
    電気設備学会誌
    2018年 38 巻 1 号 59-60
    発行日: 2018年
    公開日: 2018/01/11
    ジャーナル フリー
  • 松山 洋, 八木 克敏, 中山 大地, 鈴木 啓助
    水文・水資源学会誌
    2006年 19 巻 5 号 392-400
    発行日: 2006年
    公開日: 2006/09/19
    ジャーナル フリー
    阿蘇谷西部の難透水層は地下200 m付近にあり,これが阿蘇谷から阿蘇外輪山北麓にかけて低下していると考えられている.さらに,阿蘇谷西部の地下水や河川水がSO42-に富んでいることを考慮すると,阿蘇外輪山北麓のどこかで SO42-に富んでいる水が湧出している可能性がある.河川水質は集水域の湧水の水質を反映するので,本研究では阿蘇外輪山北麓を流れる杖立川上流域の河川水について,河川が合流する手前の本流側と支流側で水質調査を行なった.本稿ではその結果について示し,これに基づく考察を行なった.
    杖立川上流域東部を流れる田の原川や志賀瀬川では,Na+やCl-に富んだ河川水がみられ,これらは河川上流部にある温泉の影響を受けている.また,杖立川上流域西部を流れる湯田川ではSO42- に富んだ河川水がみられ,これは湯田温泉から供給されている.SO42-に富むという意味で,湯田温泉と阿蘇谷の地下水や河川水は共通しているが,湯田温泉のSiO2濃度は阿蘇谷の地下水や河川水のSiO2濃度よりも小さい.このことから,湯田温泉のSO42-に富んだ水は阿蘇谷起源であるとは言えない.
  • 山本 浩一, 末次 忠司
    水工学論文集
    2005年 49 巻 1417-1422
    発行日: 2005/02/01
    公開日: 2011/06/27
    ジャーナル フリー
    Nutrients concentrations in the sediment in the estuary of the Chikugo River were surveyed around the flood period. After the flood period, Fe-P, Al-P and Ads-P concentration increased in the sediment of the tidal flat at the front of rivers. On the other hand, concentration of these components in the sediment of the tidal flat, which is far from river mouths, did not increase. Moreover, concentrations of nitrogen and organic carbon in the sediment decreased in the tidal flat. It was clarified that the discharged sediment from the river basin affected the nutrient concentration and environment of the surface sediment in the estuary
  • 橋本 彰博, 田井 明, 小松 利光, 池畑 義人
    河川技術論文集
    2013年 19 巻 105-110
    発行日: 2013年
    公開日: 2023/03/31
    ジャーナル フリー

    Heavy rainfall which we had never experienced occurred in the northern part of Kyushu Island on July 2012. A record-breaking rainfall was observed at several stations. This heavy rainfall caused sediment disaster, river flooding and inundation that claimed many casualties and missing in Ooita, Kumamoto and Fukuoka Prefecture. In Taketa City, Ooita prefecture, two people died and more than 250 houses were inundated due to the flooding of the Tamarai River which flows through the Taketa City. Especially, the water level rose rapidly and reached about 2.5m from a top of a levee in the Haitabaru area, downstream part of the Tamarai River. A field observation and a numerical simulation were carried out in the Tamarai River Basin in order to find out the reason why the water level had risen like that. Results from calculations showed that the increase in the water level due to a decrease of just 10 percent in the cross-sectional area of the river was estimated to be 3m. Because of heavy rainfall, a large amount of driftwoods were produced in the upstream area and accumulated at the river bridge, New Azou Bridge. As a result the cross- sectional area of the river decreased and the rapid increase in the water level occurred.

  • 林 正雄, 渡辺 公一郎, 古谷 直行
    日本地熱学会誌
    1985年 7 巻 4 号 383-399
    発行日: 1985/10/25
    公開日: 2009/08/07
    ジャーナル フリー
    The strike and dip of fractures such as slickensides, hydrothermal veins and joints, found in drillcores from the Otake-Hatchobaru geothermal area have been estimated after measuring the thermo-remant magnetism of the cores with an astatic magnetmeter. The results show that most of the slickensides and veins dip southward, though their strikes vary considerably from NW-SE to NE-SW. In addition, the analysis of slickensides has revealed that the NW-SE trending faults basically are of left-handed strike slip type, while the NE-SW ones are of light-handed one. It is inferred that both kinds of faults were originally formed by the ENE-WSW compressional stress fields whose minimum stress axis dip NNW with moderate angles. Recently, the normal stress fields, whose intermediate stress axis tends NW-SE, have probably made the NW-SE trending fault planes open and permeable so that they have become the present breeding faults.
  • 水上 泰介
    農業経営研究
    1973年 11 巻 2 号 43-60
    発行日: 1973年
    公開日: 2012/10/29
    ジャーナル フリー
  • 町田 怜子, 麻生 恵
    ランドスケープ研究
    2008年 71 巻 5 号 693-696
    発行日: 2008/03/31
    公開日: 2009/05/08
    ジャーナル フリー
    Despite the diminishment of environmentally threatening development, recent social factors such as increasing local elderly population and shortage of successor of agricultural activities have instead accelerated the deterioration of secondary grassland landscapes. This research, focusing on the secondary grasslands in Aso Region, on the purpose to resolve the various problems caused by the recession of management activities that is difficult to solve by the existing national park planning, considers the criteria and evaluation method for the future landscape management of national parks. This research then proposes new evaluation methods based on the following factors : 1 various people's spatial perception pattern of the grasslands and 2 re-zoning of the grasslands according to the grassland type on the basis of macro landform, and examines the applicability to the landscape management of national parks.
  • 猪爪 範子
    造園雑誌
    1991年 55 巻 5 号 367-372
    発行日: 1991/03/31
    公開日: 2011/07/19
    ジャーナル フリー
    別府市に連なる湯布院町は, 昭和39年の九州横断道路開通を契機にして, 山間の邸びた湯治湯から, 新しい温泉観光地へと飛躍的な展開をとげる. 現在は, 来訪する観光客が年間に300万人を超える有名観光地となったが, もう一方では住民主導型の内発的地域開発によるまちづくり観光地としても希有の集積を果たした.
    このような状況にある湯布院町の観光地形成の経過を辿り, その課題となるところを明らかにすることによって, 地域に根差した息の長い観光地のあり方を提示する.
  • 糖尿病
    1971年 14 巻 3 号 172-178
    発行日: 1971/05/31
    公開日: 2011/08/10
    ジャーナル フリー
  • 飯田 夕貴, 包清 博之
    ランドスケープ研究
    2014年 77 巻 5 号 481-486
    発行日: 2014年
    公開日: 2015/05/22
    ジャーナル フリー
    The planning approach to prevailing small hydropower is still to be established. The varying characteristics of hydropower products such as type, color and shape may affect regional landscape characteristics. The objective of this study is to recognize the impact of potential landscape change by prevailing small hydropower in hilly and mountainous regions that are advantaged in water resources and natural landscape. The study areas were the Minamioguni Town and Itsuki Village in Kumamoto Prefecture. The trend in the appearance of prevailing small hydropower was assessed considering the places of generation and consumption of electricity according to the topographical analysis and was recognized through a questionnaire survey to production companies of small hydropower and local residents. As a result, it was recognized the variation of area types and planning requirements affected by the prevailing small hydropower.
  • 戸田 義宏
    造園雑誌
    1993年 57 巻 4 号 338-345
    発行日: 1993/03/26
    公開日: 2011/07/19
    ジャーナル フリー
  • 井上 克弘
    ペドロジスト
    1981年 25 巻 2 号 97-118
    発行日: 1981/12/30
    公開日: 2018/06/30
    ジャーナル フリー
    Generally, the essential clay mineral of the volcanic ash soils is characterized by a predominance of allophane, imogolite, halloysite, and gibbsite. The 14Å minerals also are, however, extensively identified in the volcanic ash soils, but there is a divergence of opinion as to their origin. The occurrence of 14Å minerals in the volcanic ash soils in the Honshu and Hokkaido districts of Japan is considered to have relations with a snowfall. The 14Å minerals in these areas are probably provided as an ice nuclei of snow from eolian dusts in the atmosphere, which are dominantly originated from China. The eolian dusts may directly fall on the ground in the Kyushu district. From the amounts of eolian dusts in the palaeosols and peat soils, the accumulation rates of eolian dusts in last glacial intervals and Holocene are estimated to be 2.1〜3.3 and 0.11〜0.80 g/cm^2/1,000 yr, respectively. The clay mineral of eolian dusts is characterized by a predominance of 14Å minerals, illite, kaolinite, and quartz. The 14Å minerals are dominant in montrnorillonite, vermiculite, and intergrades, and their contents depend on the degree of weathering. The composition of crystalline clay minerals in the volcanic ash soils resembles nearly to that of Chinese loess, eolian dusts, and the North Pacific marine sediments, although the latter contains much more illite than the 14Å minerals in comparison with the former. Probably the dominating weathering sequence of eolian dusts deposited in the soils is considered to be as follows : [chemical formula] From these results, the contribution of eolian dusts is primarily reflected in the 14Å minerals, illite, kaolinite, and quartz in the volcanic ash soils in Japan.
  • 井芹 晴香, 平松 和昭, 原田 昌佳
    農業農村工学会論文集
    2011年 79 巻 2 号 97-107
    発行日: 2011/04/25
    公開日: 2012/04/25
    ジャーナル フリー
    近年,混住化が急速に進行する筑後川流域を対象に,窒素・リンの流れを解明するため,多様な流域情報を考慮した分布型窒素・リン負荷流出モデルを開発した.その結果,各観測地点における河川流量およびTN・TPに関して,概ね良好に再現することができた.つづいて,開発したモデルを用いて,畜舎排水や処理浄化槽を対象とした排出負荷削減対策や,地形連鎖を利用した水田による水質浄化を想定したシナリオ分析を行った.その結果,土地利用形態により水質改善の傾向が異なることから,各地域における負荷排出の傾向の把握,ならびに,それに適した対策の実施が重要であることが確認できた.また,畜舎排水および水田の水質浄化機能に関するシナリオの削減率が非常に大きいことから,農業地域における対策の重要性が示唆された.
  • 地理学評論
    1966年 39 巻 3 号 176-190
    発行日: 1966/03/01
    公開日: 2008/12/24
    ジャーナル フリー
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