[S-SS13] 環境地震学の進展

[SSS13-P05] Impact of Kuroshio meander on pressure changes in 2012 to 2013 at DONET and borehole observatories along Nankai Trough

*有吉 慶介¹、永野 憲¹、長谷川 拓也²、飯沼 卓史¹、松本 浩幸¹、荒木 英一郎¹、高橋 成実³、堀 高峰¹ (1.国立研究開発法人海洋研究開発機構、2.北海道大学大学院地球環境科学研究院、3.国立研究開発法人防災科学技術研究所)

キーワード：スロースリップイベント、間隙圧、南海トラフ

Since DONET station covers above the source region of the 1944 Tonankai earthquake and its shallower extension, it has been also expected to monitor stress accumulation/release process around there from pressure gauges. Recently, it has been well known that slow slip event (SSE), which is one of slow earthquake family (Ide et al., 2007), repeatedly occurs in major subduction zones in shallower extension of the source regions of megathrust earthquakes as well as deeper one (Obara and Kato, 2019). For the shallower extension, SSE has been detected repeatedly from pore pressure extracted from the combination of pressure sensors in a borehole and on the seafloor close to DONET (Araki et al., 2017). For smaller SSE than that equivalent to Mw ~5, its crustal deformation could not be detected from inland observation networks because of small amount of displacement for long distance (Ariyoshi et al., 2021).
On the other hand, seafloor pressure gauge contains atmospheric and oceanic fluctuations in addition to leveling change due to crustal deformation (e.g., Araki et al., 2017; Ariyoshi et al., 2021). In recent studies, there are several ways to extract the crustal deformation component from pressure gauges on the seafloor and in the boreholes.
In this presentation, we reinvestigate the possible SSEs in 2012 and 2013 from the view of crustal deformation on the basis of pore pressure in the borehole and oceanic fluctuation expected from ocean modeling.