Tomographic imaging of large earthquake source zones

2023 Fiscal Year Final Research Report

• Project/Area Number: 19H01996
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: Tohoku University
• Principal Investigator: Zhao Dapeng 東北大学, 理学研究科, 教授 (70304665)
• Co-Investigator(Kenkyū-buntansha): 豊国 源知 東北大学, 理学研究科, 助教 (90626871)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 地震波トモグラフィー / 沈み込み帯 / 大地震 / 火山 / 地震波異方性 / 沈み込むスラブ / マントルウェッジ / マントルプルーム

Outline of Final Research Achievements

We determined high-resolution seismic tomography of source zones of large earthquakes in subduction zones and continental regions, which shed new light on the seismogenic structures. Significant structural heterogeneities are revealed in and around the source zones of large earthquakes. Fluids from the subducting slab dehydration can trigger large crustal earthquakes. The generation of megathrust earthquakes is controlled by both the upper and lower plates, as well as subslab hot upwelling flow. Intraslab earthquakes can be caused by reactivation of hydrated faults produced at the outer-rise before plate subduction. Fluids may be involved in the generation of most earthquakes in subduction zones. These results indicate that large earthquakes do not take place randomly at any sites, but only in anomalous areas where prominent structural heterogeneities (i.e., seismogenic structures) exist, which can be detected by high-resolution geophysical imaging.

Free Research Field

地震学、固体地球物理学

Academic Significance and Societal Importance of the Research Achievements

日本列島陸域から日本海溝までの海底に及ぶ,稠密な地震観測網で記録される膨大なデータを, 最先端の地震波トモグラフィー技術を開発・駆使して解析した.それにより,浅部から深部までの詳細な3次元構造を求め,巨大地震の発生機構・島弧火山の成因及び深部流体の移動などの沈み込みダイナミクスの解明に挑戦した.また,世界の他の沈み込み帯と大陸地域の地下３次元構造と地震・火山活動についても調べた.得られる研究成果は,日本列島のみでなく,世界の他の地域の研究にも大きなインパクトを与えるもので,世界の固体地球科学的研究への波及効果も大きい.さらに,地震・火山・津波災害の防災・減災にも重要な意味を持つ.