Precise structure at the top of subducted plate and its relationship with the plate dynamics revealed by integrated interpretation for controlled source seismic data

• Project/Area Number: 15K05264
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Solid earth and planetary physics
• Research Institution: The University of Tokyo
• Principal Investigator: IWASAKI Takaya 東京大学, 地震研究所, 教授 (70151719)
• Project Period (FY): 2015-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥3,120,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥720,000); Fiscal Year 2017: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000); Fiscal Year 2016: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2015: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
• Keywords: プレート境界構造 / 反射波 / プレート境界摩擦特性 / 制御震源地震探査 / 波形解析 / 波線理論 / 波線追跡法 / 地震波干渉法 / AVO法 / 西南日本 / 中央構造線 / 三波川帯 / 地殻構造 / プレート構造 / 拡張AVO法 / 幾何学的減衰評価 / 地震探査 / 紀伊半島

Outline of Final Research Achievements

This study aimed at developing integrated analysis method to determine the fine structure at the top of the subducted plate boundary. My method is based on the asymptotic ray theory, which was efficiently improved in this study to realize high accuracy and stability for evaluating both the travel times and amplitudes in the complex structure models. Seismic data collected in the Kii Peninsula in 2006 were reinterpreted by my method. The results obtained indicate the detailed structural variation at the top of the Philippine Sea plate and structures of the MTL and accretionary complexes in the overriding SW Japan arc crust. The reflection property at the plate boundary is significantly changed from its seismogenic part to the steady slip part. The structure in the SE Japan arc is characterized by the northward dipping reflectors. Particularly, the Sanbagawa metamorphic belt is composed of xx-km thick reflectors, whose top corresponds to the MTL.

Academic Significance and Societal Importance of the Research Achievements

本研究では，制御震源データの総合波形解析法によって，プレート境界の精密な構造推定を行うことを目指し，人工震源からの幾何学的減推を正しく評価し，プレート境界面における反射特性を求める手法を開発した．この手法は，プレート境界域にとどまらず，様々な地質構造の領域でも適用できるものである．
本研究では，紀伊半島下のプレート境界の形状，そこでの反射特性を求めた．このような知見は，単にプレート境界構造だけでなく，この領域で発生する巨大地震の理解に貢献するものである．また，上盤側島弧において明らかになった構造は，島弧地殻発達のプロセスの理解に重要である．

Research Products

• [Presentation] New findings on the subducted Philippine Sea plate and the overriding SW Japan arc by reinterpretation of previous seismic data in Kii Peninsula (2018)
  • Author(s): Iwasaki, T., Kurashimo, E., Abe, S., Yokota, K., Iidaka, T., Katao, H., Higashinaka, M., Ito, K., Hirata, N., Sato, H., Ito, T., Nakanishi, A., Kaneda, Y.
  • Organizer: 18-th SEISMIX International Symposium (International Symposium on Multi-scale Seismic Imaging of the Earth's crust and Upper Mantle)
• [Presentation] Detailed structures of the subducted Philippine Sea plate and the overriding SW Japan arc - New findings from reinterpretation of previously obtained seismic data with modern processing techniques- (2018)
  • Author(s): 岩崎貴哉・蔵下英司・阿部進・横田健・飯高隆・片尾浩・東中基倫・伊藤潔・平田直・佐藤比呂志・伊藤谷生・仲西理子・金田義行
  • Organizer: 日本地球惑星科学連合2018大会
• [Presentation] Imaging of the subducted Philippine Sea plate and the overriding SW Japan arc - Reinterpretation of the wide-angle reflection data in the Kii Peninsula, SW Japan (2017)
  • Author(s): Iwasaki, T., Abe, S., Kurashimo, E., Yokota, K., Iidaka, T., Katao, H., Higashinaka, M., Nakanishi, A., & Kaneda, Y.
  • Organizer: IAG-IASPEI 2017
  • Int'l Joint Research
• [Presentation] Seismological structures of the subducted Philippine Sea plate and the overriding SW Japan arc, - Reinterpretation of the wide-angle reflection data in the Kii Peninsula, SW Japan - (2017)
  • Author(s): Iwasaki,T., Kurashimo, E., Abe, S., Yokota, K., Iidaka, T., Katao, H., Higashinaka, M., Nakanishi, A., & Kaneda, Y.
  • Organizer: EGU 2017
• [Presentation] Structures of the subducted Philippine Sea plate and the overriding SW Japan arc from reprocessing of seismic wide-angle reflection data in Kii Peninsula, SW Japan (2017)
  • Author(s): Iwasaki, T., Abe, A., Kurashimo, E., Yokota, K.., Iidaka, T., Katao, H., Higashinaka, M., Nakanishi, A. & Kaneda, Y.
  • Organizer: JPGU-AGU Joint Meeting 2017
• [Presentation] 地震波干渉法による2006年紀伊半島東部構造探査の再解析 (2016)
  • Author(s): 岩﨑貴哉・飯高隆・蔵下英司・阿部進・横田健・東中基倫・片尾浩・仲西理子・金田義行
  • Organizer: 日本地震学会2016年秋季大会
  • Place of Presentation: 名古屋国際会議場(愛知県名古屋市)
  • Year and Date: 2016-10-05
• [Presentation] 地表散乱波に対する地震波干渉法解析を通じた稠密反射記録の再構築による地殻構造イメージング (2016)
  • Author(s): 阿部進・清水英彦・東中基倫・岩﨑貴哉・飯高隆・蔵下英司・佐藤比呂志
  • Organizer: 日本地震学会2016年秋季大会
  • Place of Presentation: 名古屋国際会議場(愛知県名古屋市)
  • Year and Date: 2016-10-05