日本地球惑星科学連合2019年大会

講演情報

[J] ポスター発表

セッション記号 S (固体地球科学) » S-SS 地震学

[S-SS14] 地震発生の物理・断層のレオロジー

2019年5月29日(水) 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:岡崎 啓史(海洋研究開発機構)、向吉 秀樹(島根大学大学院総合理工学研究科地球資源環境学領域)、野田 博之(京都大学防災研究所)、吉田 圭佑(東北大学理学研究科附属地震噴火予知研究観測センター)

[SSS14-P04] 半遠洋性堆積物の続成作用に伴う摩擦・透水特性の変化

*岡崎 啓史1片山 郁夫2山口 飛鳥3 (1.海洋研究開発機構高知コア研究所、2.広島大学大学院地球惑星システム学専攻、3.東京大学大気海洋研究所)

キーワード:沈み込み帯、摩擦特性

Deployments of seismic and geodetic observation networks had revealed the activity of slow earthquakes along the subduction plate boundaries, which are characterized as intermediate fault slip rate between earthquake (~1m/s) and stable sliding along the plate boundary (~1 nm/s). Diagenesis of subducting sediments has stimulated interest in their relationship to regular and slow seismicity in the subduction zone. We report experimental results on the effect of diagenetic reactions to hydraulic and frictional properties of incoming hemipelagic sediments. Hemipelagic sediments taken from KS-15-3 Shinseimaru cruise are used as the starting sample. Friction experiments and permeability measurements were carried out with a confining pressure of 150 MPa and a pore pressure of 58 MPa and temperatures ranging RT–230 degC. When the sample is sheared immediately after reaching the experimental condition, all experimental data at the temperature below 150 degC showed a velocity-strengthening behavior. On the other hand, at the temperature of 230 degC, the frictional behavior is no longer stable, but stick-slip behavior was observed during the experiments. We also measured a time-dependent permeability evolution of hemipelagic sediments to assess how diagenetic reactions consolidate the sediments. Permeability decreased about an order magnitude due to the mechanical compaction from the effective pressure of 3 MPa to 92 MPa, and decrease additional an order magnitude of permeability is observed during the hot-pressing of the sample at the pressure and the temperature of 92 MPa and 100 degC, respectively. Those experimental observations suggest that thermally activated compactions, possibly pressure solution creep, could contribute key role for understanding the physical property of subducting sediments.