表層堆積物の変形構造からみた深谷断層系綾瀬川断層北部の後期更新世以降の活動史  [in Japanese] Paleoseismic History of the Northern Ayasegawa Fault since the Late Pleistocene Reconstructed from Shallow Sub-surface Deformation Structure  [in Japanese]

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Author(s)

    • 須貝 俊彦 SUGAI Toshihiko
    • 東京大学大学院新領域創成科学研究科自然環境学専攻 Department of Natural Environmental Studies, Graduate School of Frontier Sciences, the University of Tokyo
    • 水野 清秀 MIZUNO Kiyohide
    • 産業技術総合研究所地質調査総合センター Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology
    • 石山 達也 ISHIYAMA Tatsuya
    • 産業技術総合研究所活断層研究センター Active Fault Research Center, National Institute of Advanced Industrial Science and Technology
    • 杉山 雄一 SUGIYAMA Yuichi
    • 産業技術総合研究所活断層研究センター Active Fault Research Center, National Institute of Advanced Industrial Science and Technology
    • 松島 紘子 MATSUSHIMA Hiroko
    • 東京大学大学院新領域創成科学研究科自然環境学専攻 Department of Natural Environmental Studies, Graduate School of Frontier Sciences, the University of Tokyo
    • 吉田 英嗣 YOSHIDA Hidetsugu
    • 東京大学大学院新領域創成科学研究科自然環境学専攻 Department of Natural Environmental Studies, Graduate School of Frontier Sciences, the University of Tokyo
    • 山口 正秋 YAMAGUCHI Masaaki
    • 産業技術総合研究所地質調査総合センター Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology
    • 大上 隆史 OGAMI Takashi
    • 東京大学大学院新領域創成科学研究科自然環境学専攻 Department of Natural Environmental Studies, Graduate School of Frontier Sciences, the University of Tokyo

Abstract

The northern Ayasegawa fault is a part of the Fukaya fault system, which is the longest active fault in the Kanto district. The paleoseismology of the northern Ayasegawa fault was revealed by a combination of arrayed boring and ground penetrating radar (GPR) survey. The northern Ayasegawa fault produced a fold scarp with the NW-SE direction running along the boundary between the Oomiya 2 (O2) surface and fluvial lowland. The O2 was formed in Marine Isotope Stage 5a, and was slightly deformed with a wide warping zone. Sixteen sediment cores arrayed across the warping zone contain a series of tephra layers such as Hk-TP (<I>ca</I>. 60-65 ka), KMP, AT (26-29 ka), As-BP group (20-25 ka), and As-YP (15-16.5 ka). These key beds except Hk-TP were deposited and deformed parallel to each other, suggesting that no faulting events occurred between KMP and As-VP fall. The timing of the last faulting event is after the As-YP fall, and is probably younger than 10 ka based on an interpretation of GPR profiles and 14C ages. KMP should be deposited horizontally because it intervened in the peaty silt layer, which accumulated conformably on lacustrine deposits overlapping the fold scarp. Thus, the KMP horizon roughly indicates the vertical offset produced by the events occurred after the As YP fall. The events were probably singular, and the last one formed a vertical offset of more than 4 m. The older event occurred at around 70 ka between Hk-TP fall and O2 formation. Vertical deformation of the O2 was at least 7 m, indicating the possibility that the vertical offset caused by the penultimate event is at least 3 m. The vertical slip per event might reach 5 m, and the average vertical slip rate is nearly 0.1 mm/yr because the warping zone detected by the arrayed boring above is within the flexure zone shown by the P-wave seismic profile. The northern Ayasegawa fault is considered to be a single behavioral segment because of its longer recurrence interval and lower slip rate of 0.1 mm/yr in comparison with those of the other part of the Fukaya fault system.

Journal

  • Journal of Geography (Chigaku Zasshi)

    Journal of Geography (Chigaku Zasshi) 116(3), 394-409, 2007-08-25

    Tokyo Geographical Society

References:  26

Cited by:  4

Codes

  • NII Article ID (NAID)
    10025676750
  • NII NACSIS-CAT ID (NCID)
    AN00322536
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    0022135X
  • NDL Article ID
    8941452
  • NDL Source Classification
    ZM41(科学技術--地球科学)
  • NDL Call No.
    Z15-169
  • Data Source
    CJP  CJPref  NDL  J-STAGE 
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