日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 S (固体地球科学) » S-CG 固体地球科学複合領域・一般

[S-CG50] Intraslab and intraplate earthquakes

2019年5月30日(木) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:北 佐枝子(建築研究所)、大内 智博(愛媛大学地球深部ダイナミクス研究センター)、Marcel Thielmann(Bavarian Geoinstitute, University of Bayreuth)、奥脇 亮(産業技術総合研究所 地質調査総合センター 活断層・火山研究部門)

[SCG50-P02] Inhomogeneous conduit across slab controlled by intraslab stress heterogeneity in the Nankai subduction zone

*大坪 誠1宮川 歩夢2片山 郁夫3岡崎 啓史4 (1.産業技術総合研究所 活断層・火山研究部門、2.産業技術総合研究所 地質情報研究部門、3.広島大学大学院理学研究科、4.海洋研究開発機構 高知コア研究所)

キーワード:流体、南海トラフ、スラブ、スロー地震、応力

Non volcanic deep low-frequency tremors and slow slip events occur simultaneously in the transition zone from locked to continuously creeping fault at the down dip portion of the Nankai Trough subduction zone, southwestern Japan. The occurrence of these slow earthquakes is attributed to the effect of high pore pressures on the plate boundaries. The Nankai Trough subduction zone has a discontinuous band of occurrence of these slow earthquakes along the trench. Here we show that spatial variation of intraslab stress can control fluid migration through the subducted Philippine Sea slab to the plate boundary. The tri-axial normal faulting stress detected by the stress tensor inversion by using focal mechanisms in the slab controls anisotropies of permeability trending NNW–SSE sub-horizontal orientation from the subducted Philippine Sea slab to the plate boundary. The inhomogeneous condition controlled by the spatial stress heterogeneities in the subducted Philippine Sea slab represents the intraslab fluid pathway. The hypothesis is consistent with spatial heterogeneity of slow earthquake activities and 3He/4He ratio distributions.