2025-05-26 九州大学
図１ 熊本地震前の活動から見た、深さ10－20㎞のb値と臨界度活動指標分布
＜関連情報＞
- https://www.kyushu-u.ac.jp/ja/researches/view/1271
- https://www.kyushu-u.ac.jp/f/61809/25_0526_02.pdf
- https://www.nature.com/articles/s41598-025-01595-x
地震モーメント効率と小地震の頻度-回数分布が示す大地震の近接性 LARGE earthquake proximity indicated by seismic moment efficiency and frequency-number distribution of small earthquakes
Satoshi Matsumoto
Scientific Reports Published:19 May 2025
DOI:https://doi.org/10.1038/s41598-025-01595-x
Abstract
The size distribution of minor earthquakes, characterized by a power-law decay (b-value), sometimes indicates the hazard information of major earthquakes. Studies show that the b-value reflects the stress level and proximity of the fault failure condition. However, the mechanisms are difficult to determine. This study proposes an additional proximity indicator that is ratio of stacked seismic moment tensor to total moment release in a volume. The ratio indicates efficiency of inelastic strain due to seismic moment release by earthquakes, being close to the strength of the medium based on the Mohr diagram and Coulomb failure condition. We examined the b-value and efficiency variations in pre- and post-seismic activities of the 2016 Kumamoto earthquake sequence. The weighted b-value distribution based on efficiency captured the initiation point of the Kumamoto earthquake. Thus, utilizing both b-value and efficiency can improve earthquake alerts and disaster mitigation.
