東日本太平洋沖地震後の余効変動解析へ向けた東北日本弧レオロジー断面  [in Japanese] Rheological profile across the northeastern Japan lithosphere toward precise modeling of the 2011 Tohoku Oki Earthquake  [in Japanese]

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Author(s)

    • 武藤 潤 Muto Jun
    • 東北大学大学院理学研究科地学専攻 Department of Earth Sciences, Tohoku University
    • 大園 真子 Ohzono Mako
    • 北海道大学大学院理学研究院付属地震火山研究観測センター Institute of Seismology and Volcanology, Hokkaido University

Abstract

東北地方太平洋沖地震後の余効変動の定量的解析にとって重要な東北日本弧の東西レオロジー強度断面を,地球物理学的観測および近年の実験岩石力学結果を用いて作成した.得られた強度プロファイルは,地震前に得られていた奥羽脊梁山脈への測地学的歪み集中や地震の深さ変化を説明する.さらにプレート境界型地震から推定される応力変化量を仮定することで,東北日本弧の粘性構造を求めた.地球物理学的観測から推定されている部分溶融帯や断層深部延長など低強度帯の存在は,内陸地震後の余効変動から推定された東北日本弧の粘性率を説明する.異なる余効変動機構の分離とそれぞれの定量的解析には,東北日本弧粘性構造の著しい不均質性を考慮する必要がある.

A two-dimensional rheological profile crossing the northeastern Japan arc was created to evaluate and distinguish various styles of post-seismic deformation relating to the 2011 Tohoku-Oki earthquake. The calculated profile is based on recent rock-mechanics studies and geophysical observations that explain observed patterns of geodetic strain accumulation and shallow seismicity prior to the earthquake. Viscosities were then calculated assuming stress-change magnitudes commonly associated with interplate earthquakes. Recently derived flow laws for various rocks and minerals predict the presence of weak zones that developed via processes likely operating in the lithosphere (e.g., partial melting and shear zone development). Strain localization into weak zones explains low viscosity estimates (10<sup>18</sup>—10<sup>20</sup> Pas) from post-seismic creep after inland earthquake events. Our calculations reveal significant lateral variations in strengths and viscosities across the northeastern Japan arc. These viscoelastic lithospheric structures should be taken into account in order to differentiate viscous relaxation from other post-seismic deformation processes.

Journal

  • The Journal of the Geological Society of Japan

    The Journal of the Geological Society of Japan 118(5), 323-333, 2012

    The Geological Society of Japan

Codes

  • NII Article ID (NAID)
    130002530854
  • NII NACSIS-CAT ID (NCID)
    AN00141768
  • Text Lang
    JPN
  • ISSN
    0016-7630
  • NDL Article ID
    023816656
  • NDL Call No.
    Z15-174
  • Data Source
    NDL  J-STAGE 
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