Analysis of surface reworking volcanic ash deposit crossing Matoishi Bokujo I active fault, NW Aso caldera, Japan

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Other Title
  • 阿蘇カルデラ北西部・的石牧場Ⅰ断層上の表層火山灰再堆積物の分析

Abstract

2016 Kumamoto Earthquake was triggered by the movement of Higagu and Futagawa Faults. Previous studies reported that the earthquake deformed landform around Matoishi Bokujo I active normal fault, where is 10 km north of Futagawa Fault and whose strike is EW. However, Matoishi Bokujo I active fault is not identified as seismogenic fault. This Matoishi Bokujo I active fault forms flecure scarp facing south; i.e., mountain and valley side is north and south, respectively. This analysis measured reflactive index of volcanic glass, included in the suface reworking volcanic ash layer. The glasses were sampled in the two arrayes, i.e., valley side and mountain side. Judging from reflective index and microscopic observation, AT glasses (26,000 years BP) and K-Ah glasses (7,300 years BP) were identifed. Count ratio of AT glasses / K-Ah glasses was more in valley side samples than in mountain side samples. We think that K-Ah volcanic ash was washed out from the mountain slope; therefore, we concluded that flecure scarp existed at the K-Ah falling age.

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Details 詳細情報について

  • CRID
    1390845713074394112
  • NII Article ID
    130007628517
  • DOI
    10.14866/ajg.2019s.0_274
  • Text Lang
    ja
  • Data Source
    • JaLC
    • CiNii Articles
  • Abstract License Flag
    Disallowed

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