2011年東北地方太平洋沖地震による津波の堆積作用と堆積物::広田湾と仙台湾の事例を中心とする検討  [in Japanese] Tsunami sedimentation and deposits due to the 2011 Tohoku earthquake::a review of case studies from Sendai and Hirota Bays  [in Japanese]

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Abstract

<p>本稿では,2011年東北地方太平洋沖地震の津波について,特に土砂の動態や収支,水理量と堆積物の関係に着目し,異なる地形・津波の特徴をもつ二つの地域を対象に,これまでの調査・研究による知見を整理した.三陸沿岸の広田湾では,海域から陸上への堆積物の移動が起こったことが古生物学的データ,ビデオ映像および数値解析によって明らかにされた.また,引き波の影響が大きく,巨視的には沖合方向への堆積物の移動距離と量が卓越する特徴を持つ.一方,仙台湾沿岸では,海底から陸上への堆積物の移動は非常に限られていたことが,地質学的データおよびビデオ映像と数値解析によって示された.また,砂質堆積物の沖合方向と内陸方向への移動距離は同程度であった.津波堆積作用における両地域の差は,主に陸上・海底地形と津波の波形の違いによって生じた.</p>

<p>This review summarizes geological research on the tsunami caused by the 2011 Tohoku Earthquake, with a focus on the sediment dynamics and budget, and relationship between hydraulics and deposit characteristics, in two areas with different settings. The tsunami sedimentation in Hirota Bay, Sanriku Coast, was characterized by offshore transport of beach sediments due to an intensive backwash. Onshore transport of marine sediments was inferred from paleontological data, as well as visual observations and numerical modeling of the tsunami. In contrast, geological evidence, video footage, and numerical modeling suggest that onshore transport of marine sediments was limited in Sendai Bay. These differences are best explained by the topographic and bathymetric settings of these sites, and the properties of the tsunami wave. The field of tsunami sedimentology has been significantly advanced through geological studies of the Tohoku tsunami deposits. Further challenges are identified regarding the application of the Tohoku tsunami deposit research to paleotsunami studies and hazard assessment.</p>

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  • The Journal of the Geological Society of Japan

    The Journal of the Geological Society of Japan 123(10), 781-804, 2017

    The Geological Society of Japan

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