2026-09-02 産業技術総合研究所
※図は原論文の計算結果を元に新たに作図しています。
＜関連情報＞
- https://www.aist.go.jp/aist_j/press_release/pr2026/pr20260902/pr20260902.html
- https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025JB032509
プレート内地震と測地データを用いたプレート結合の年々変動および微細スケール変動の検出：東北地方太平洋沖プレート境界への応用 Detection of Interannual and Fine-Scale Plate Coupling Variations Using Intraplate Earthquakes and Geodetic Data: Application to the Tohoku-Oki Plate Boundary
Kazutoshi Imanishi, Akemi Noda
Journal of Geophysical Research: Solid Earth Published: 01 September 2026
DOI:https://doi.org/10.1029/2025JB032509
Abstract
We propose a method to infer detailed spatiotemporal variations in interplate coupling by integrating geodetic and seismic data. It examines whether focal mechanisms of intraplate earthquakes occurring near the plate interface align with the stressing rates caused by a geodetically derived slip-deficit rate model, evaluating deviations from a steady coupling state. We apply this method to the Tohoku-Oki plate boundary region over a quarter-century period, including the 2011 Mw9.0 Tohoku-Oki earthquake. The analysis successfully detects previously reported features, such as the partial decoupling of the plate interface in the large slip area of the Tohoku-Oki earthquake in the years leading up to the event, and the decadal evolution of aseismic slip off the coast of central and southern Tohoku before the Tohoku-Oki earthquake. Additionally, it reveals complex variations in the interplate coupling, including temporal fluctuations and fine-scale spatial heterogeneities not clearly captured by geodetic data alone. These findings highlight the value of integrating focal mechanism and geodetic information for a refined understanding of the evolving coupling state along subduction zones. Our method allows detection of changes on interannual timescale and spatial variations at scales finer than those typically resolved by geodetic inversions. This provides a powerful new tool for monitoring interplate coupling evolution, offering potential improvements in seismic hazard assessment and early identification of anomalous coupling patterns that may precede large earthquakes.
