[S-SS27] 地震発生の物理・断層のレオロジー

[SSS27-22] 脆性・塑性遷移における有効応力則: 岩塩を用いたアナログ実験

★招待講演

*野田 博之¹、高橋 美紀² (1.海洋研究開発機構、2.産業技術総合研究所)

キーワード：有効応力則、脆性・塑性遷移、摩擦実験

We investigated the effect of pore pressure P_f near the brittle-plastic transition (BPT) for a halite (NaCl) shear zone. Our series of precut friction experiments with a gas-medium apparatus with temperature T≤200°C, confining gas pressure P_c≤150 MPa, and P_f≤140 MPa revealed that a tanh connection between the brittle and plastic regimes works well even at elevated P_f, with a coefficient for P_f in an effective stress law α being unity. Plastic deformation around the real contacts independent of the mean stress results in α=1 regardless of the ratio of the real contact area A_r/A. The functional dependency of the shear strength on the effective normal stress may deviate from a linear dependency with increasing A_r/A. The present findings support a smooth transition in a hypothetical steady-state strength profile around a BPT, providing new insights in geologically obtained paleo-stress data in exhumed mylonitic shear zones.