磐梯火山・翁島岩屑なだれを生じた山体崩壊量の再検討 : 1888年の崩壊との比較  [in Japanese] Reexamination of Volume Loss due to the Catastrophic Sector-Collapse Causing the Okinajima Debris Avalanche of Bandai Volcano, Japan  [in Japanese]

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Abstract

This research discusses the volumetric magnitude of the catastrophic sector-collapse of Bandai volcano occurred in the late Pleistocene. The collapse produced the huge-scale rockslide-debris avalanche deposits named as the Okinajima debris avalanche. The collapse had occurred at the southwestern part of the volcano, and the Okinajima debris avalanche rushed down into the Inawashiro and the Aizu basins and deposited there. Along with the conspicuous hummocky landforms observed now, we can recognize the remnant topography of horseshoe caldera on the southwestern sector of volcanic edifice. Some previous researches indicate that the collapse volume (or depositional volume) reaches 4 cubic kilometer (km^3) or more. In regard to the catastrophic collapse volume at the Bandai volcano, the author has once examined another event occurred in 1888 A.D., the smaller one. By focusing on the size-distance distribution pattern of debris avalanche hummocks, it is evaluated the appropriateness for the volume estimation of the 1888 collapse as ca. 0.49 km^3 which is the value estimated by the previous study. Based on this implication, in the present research, the author offers new insights that the collapse volume is significantly smaller than 4 km^3 once estimated as; collapse volume is not likely to exceed beyond ca. 3.2 km^3, calculated from the dimensions of the volcanic body and the source area; scar size is approximately five times larger than that of the 1888 collapse, which amounts to the collapse volume of the Okinajima event of ca. 2.5 km^3 at a maximum, referred to ca. 0.5 km^3 of the 1888 event; according to the empirical relationship proposed by the author's previous results and the distribution pattern of the Okinajima's hummocks, the loss volume by the collapse is expected as ca. 2.0 km^3. In conclusion, the loss volume of the southern volcanic edifice due to the Pleistocene catastrophic collapse should be a half of the value previously considered.

Journal

  • 地形 = Transactions, Japanese Geomorphological Union

    地形 = Transactions, Japanese Geomorphological Union 34(1), 1-19, 2013-01-25

    日本地形学連合

References:  42

Codes

  • NII Article ID (NAID)
    110009594199
  • NII NACSIS-CAT ID (NCID)
    AN00333248
  • Text Lang
    JPN
  • Article Type
    ART
  • ISSN
    03891755
  • NDL Article ID
    024294391
  • NDL Call No.
    Z15-386
  • Data Source
    CJP  NDL  NII-ELS  NDL-Digital 
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