Increasing detection efficiency and quantifying activities of shallow tectonic tremors

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K13639
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: National Institute of Advanced Industrial Science and Technology (2019-2020); Japan Agency for Marine-Earth Science and Technology (2018)
• Principal Investigator: Yabe Suguru 国立研究開発法人産業技術総合研究所, 地質調査総合センター, 研究員 (30802699)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: スロー地震 / 南海トラフ / 日本海溝

Outline of Final Research Achievements

Slow earthquakes are fault motions different from regular earthquakes in many ways, which have been detected around Japan. Slow earthquakes at 30 km depth at the Nankai Trough are called "deep" slow earthquakes, whereas slow earthquakes at the 10 - 20 km depth at the Nankai Trough and the Japan Trench are called "shallow" slow earthquakes. This study investigated event size of shallow slow earthquakes and compared with results of deep slow earthquakes in the past studies. As a result, shallow and deep slow earthquakes, which occur at very different temperature and pressure condition, have differences in the maximum event size and commonalities in the efficiency in seismic wave radiation.

Free Research Field

地震学

Academic Significance and Societal Importance of the Research Achievements

スロー地震は沈み込み帯の歪蓄積・解放プロセスの一翼を担っているため，その活動を把握することが将来の巨大地震発生の検討に向けて重要である．陸上の観測網で捉えられる深部スロー地震は20年を超える観測実績がある一方，海域の観測網で捉えられる浅部スロー地震の観測の歴史は浅い．海域観測が整備される以前の浅部スロー地震活動を陸上観測網を用いて復元する試みがされているが，本研究結果は陸上観測網で検出されないことが必ずしも現象が発生していないことを意味しないということを指摘しており，これまでの研究の解釈に注意を喚起している．