エアガン人工地震探査による東北日本前弧域の地殻深部構造  [in Japanese] Deep Crustal Structure of the Northeastern Japan Forearc by a Seismic Exploration Using an Airgun-array  [in Japanese]

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Author(s)

    • 伊藤 亜妃 ITO Aki
    • 東北大学大学院理学研究科地震・噴火予知研究観測センター Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University
    • 日野 亮太 HINO Ryota
    • 東北大学大学院理学研究科地震・噴火予知研究観測センター Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University
    • 西野 実 [他] NISHINO Minoru
    • 東北大学大学院理学研究科地震・噴火予知研究観測センター Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University
    • 藤本 博巳 FUJIMOTO Hiromi
    • 東北大学大学院理学研究科地震・噴火予知研究観測センター Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University
    • 三浦 誠一 MIURA Seiichi
    • 海洋科学技術センター固体地球統合フロンティア研究システム Institute for Frontier Research on Earth Evolution (IFREE) Japan Marine Science and Technology Center
    • 小平 秀一 KODAIRA Shuichi
    • 海洋科学技術センター固体地球統合フロンティア研究システム Institute for Frontier Research on Earth Evolution (IFREE) Japan Marine Science and Technology Center

Abstract

In August 1999, we made a marine-land cooperative seismic experiment in the forearc region of the northeastern Japan to clarify seismic structure in the source region of the 1978 Miyagi-oki earthquake. At land seismic stations, we observed prominent later arrivals interpreted as the wide angle reflections from deeper part of the crust of the overriding NE Japan arc and also from the subducting Pacific plate. To locate these reflectors precisely, we inverted first arrival time data obtained at both land and ocean bottom stations for P wave velocity (<I>V</I><SUB>p</SUB>) distribution. Using the thus estimated <I>V</I><SUB>p</SUB> structure model, we mapped the seismic reflectors corresponding to the observed reflection arrivals. Among these reflectors, the Moho of the NE Japan arc was found to shallow towards the east, from 34km beneath the coastal line to about 20km at 70km off the shoreline. The estimated Moho depth beneath the coast is larger by about 5km than those in the previously presented crustal models and there is a strong intra-crustal reflector at Moho depths in these previously presented models. We also found two landward dipping parallel reflectors in the upper mantle, at a depth range of about 30-60km. The location of the shallow one coincides with the focal depth distribution of the interplate seismicity in this area, suggesting that this is the plate boundary, the rupture plane of the 1978 Miyagi-oki interplate earthquake. The deeper one, located less than 10 km deeper than the plate boundary, should be the Moho of the subducting oceanic crust.

Journal

  • Zisin (Journal of the Seismological Society of Japan. 2nd ser.)

    Zisin (Journal of the Seismological Society of Japan. 2nd ser.) 54(4), 507-520, 2002-04-01

    SEISMOLOGICAL SOCIETY OF JAPAN

References:  20

Cited by:  4

Codes

  • NII Article ID (NAID)
    10008205207
  • NII NACSIS-CAT ID (NCID)
    AN00305741
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    00371114
  • NDL Article ID
    6561833
  • NDL Source Classification
    ZM41(科学技術--地球科学)
  • NDL Call No.
    Z15-199
  • Data Source
    CJP  CJPref  NDL  J-STAGE 
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