[S-CG58] 岩石―流体相互作用の新展開：表層から沈み込み帯深部まで

[SCG58-P12] Experimental study on Kinetically Controlled Stick-slip Behaviors of Simulated Gypsum Gouges with Dehydration

*武藤 潤¹、川畑 樹大¹、長濱 裕幸¹、白石 令¹、佐々木 勇人²、岩崎 将明³ (1.東北大学大学院理学研究科地学専攻、2.海城中学高等学校、3.株式会社ダイヤコンサルタント)

キーワード：脱水不安定性、含水鉱物、間隙流体圧、反応速度論、脱水脆性化

Pore fluid pressure generated by dehydration of hydrous minerals can trigger deep and intermediate-depth earthquakes. Therefore, it is essential to investigate its effect on frictional behaviors. We conducted friction experiments on simulated bassanite gouges (hemihydrate gypsum) and observed the stress drops and recurrence intervals of stick-slip events decreased over time under 200 MPa and 110 °C. Microstructural observations indicates that gouges deformed under room temperature shows the development of numerous shear bands including Riedel shears. On the other hand, a sample deformed under 200 MPa and 110 °C had few Riedel shear planes, indicative of the elevated pore fluid pressure suppressing the development of shear planes in the experiment. Additionally, assuming pore fluid pressure, frictional coefficients were estimated to be approximately 0.6, consistent with previous experimental study. We derived time function of dehydration-driven pore fluid pressure evolution using Avrami kinetics. Because of the mathematical similarity of Avrami equation on the fractal geometry on the surface of reaction products (water and anhydrate) to Weibull cumulative distribution function of failure rate, we discuss the kinetics-driven pore fluid pressure evolution controlled the stick-slip behaviors of the gypsum gouges under dehydration.