Construction of three-dimensional seismic wave-speed structure for reproduction of seismic waveforms

• Project/Area Number: 16K21699
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Solid earth and planetary physics; Natural disaster / Disaster prevention science
• Research Institution: National Research Institute for Earth Science and Disaster Prevention (2017-2018); The University of Tokyo (2016)
• Principal Investigator: Miyoshi Takayuki 国立研究開発法人防災科学技術研究所, 地震津波火山ネットワークセンター, 主幹研究員 (20452500)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥3,510,000 (Direct Cost: ¥2,700,000、Indirect Cost: ¥810,000); Fiscal Year 2018: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2017: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2016: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
• Keywords: 波形インバージョン / アジョイントトモグラフィー / 関東盆地 / 広帯域地震波形 / 内部構造 / 地震動

Outline of Final Research Achievements

The three-dimensional seismic wave-speed structure was constructed by waveform inversion. Forward and adjoint simulations by large parallel computing were performed iteratively 16 times in order to infer the structure beneath the Kanto region using displacement waveforms of the period range of 5-30 sec. The new model reveals several anomalous areas with extremely low shear wave-speed in comparison with those of the initial model. These areas were found to correspond to geological features, earthquake sources, and volcanic regions. The final model better reproduced the observation than the initial model.

Academic Significance and Societal Importance of the Research Achievements

これまでは、地震波速度構造モデルは自然地震の地震動や探査による振動の到着時刻を用いて推定されてきたが、本研究では地震波形を用いて推定した。本研究で推定したモデルは、観測波形の再現を定量的に保証しつつ、構造モデルの地球科学的解釈が可能であるという意味で学術的意義が高い。また、地震動予測のためには観測波形の再現は必須であり、帯域は限られるが地震動予測が可能な三次元構造モデルが構築できたことに社会的意義がある。

Research Products

• [Journal Article] Adjoint tomography of the crust and upper mantle structure beneath the Kanto region using broadband seismograms (2017)
  • Author(s): Takayuki Miyoshi, Masayuki Obayashi, Daniel Peter, Yoko Tono and Seiji Tsuboi
  • Journal Title: Progress in Earth and Planetary Science Volume: 4 Issue: 1
  • DOI: 10.1186/s40645-017-0143-8
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Presentation] Toward adjoint tomography of the large low seismic velocity provinces beneath the western Pacific Ocean (2019)
  • Author(s): Masayuki Obayashi, Takayuki Miyoshi, Junko Yoshimitsu
  • Organizer: Joint symposium of Misasa 2019 & Core-Mantle Coevolution
  • Int'l Joint Research
• [Presentation] Construction of the seismic wave-speed model by adjoint tomography beneath the Japanese metropolitan area (2017)
  • Author(s): Takayuki Miyoshi
  • Organizer: European Geosciences Union General Assembly 2017
  • Int'l Joint Research
• [Presentation] 広帯域地震波形を用いた関東地域のアジョイントトモグラフィー (2017)
  • Author(s): 三好崇之
  • Organizer: 日本地球惑星科学連合2017年大会
• [Presentation] 京コンピュータによる全球理論地震波形計算 (2017)
  • Author(s): 坪井誠司・安藤和人・三好崇之・Daniel Peter・Dimitri Komatitsch・Jeroen Tromp
  • Organizer: 日本地球惑星科学連合2017年大会
• [Presentation] Adjoint tomography and centroid-moment tensor inversion of the Kanto region, Japan (2017)
  • Author(s): Takayuki Miyoshi
  • Organizer: American Geophysical Union 2017 Fall Meeting
  • Int'l Joint Research
• [Presentation] アジョイントトモグラフィーと日本列島の地震波速度構造への適用 (2016)
  • Author(s): 三好崇之
  • Organizer: 日本地球惑星科学連合2016年大会
  • Place of Presentation: 幕張メッセ（千葉県・千葉市）
  • Invited