Elucidation of source images of large earthquakes with a new source inversion method considering theoretical errors

2021 Fiscal Year Final Research Report

• Project/Area Number: 17K14384
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Solid earth and planetary physics
• Research Institution: National Research Institute for Earth Science and Disaster Prevention
• Principal Investigator: Kubo Hisahiko 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, 主任研究員 (00795221)
• Project Period (FY): 2017-04-01 – 2022-03-31
• Keywords: トランスディメンジョナルインバージョン / 震源過程解 / 大地震の断層破壊過程 / 地殻変動記録 / 地震波形記録

Outline of Final Research Achievements

Focusing on theoretical errors caused by the discretization of earthquake fault and the slip smoothing constraint in source inversion, which have been overlooked in previous studies, we introduced trans-dimensional inversion, which estimates the dimensions of the model parameters as well as the values of the model parameters, to the source inversion using geodetic data or seismic waveforms. The application to actual records including the 2015 Nepal Gorkha earthquake and synthetic tests demonstrated that the trans-dimensional source inversion can provide reasonable solutions composed only of meaningful slips, which were required to explain the data. The spatial relationship between the coseismic rupture extents of normal large earthquakes and the active areas of slow earthquakes along the Japan trench was also clarified.

Free Research Field

地震学

Academic Significance and Societal Importance of the Research Achievements

本研究は震源過程解析の従来手法が抱えていた課題を明らかにするとともに、トランスディメンジョナルインバージョンを震源過程解析に用いることの有用性を明らかにしたものであり、この新たな震源過程解析のアプローチは今後も継続的な研究発展および新たな知見の獲得が望まれる。また地球物理学分野における他の逆問題への波及効果も期待される。本研究で得られたプレート境界で起きる大地震および諸現象の関係についての知見は、将来発生しうる大地震を今後考えていく上で有用な情報であると考える。