Recent seismic and ocean-drilling data at the Japan Trench subduction zone suggest that the plate-boundary thrust is located within opaline chert in some places. Because seismogenic faulting along the plate-boundary thrust is known to be temperature-dependent, we investigated temperature-dependent frictional properties of opal gouge and their relevance to faulting in opaline chert at the Japan Trench subduction zone. For this purpose, we conducted triaxial friction experiments on opal gouge at a confining pressure of 150 MPa, a pore-water pressure of 50 MPa, temperatures (T) of 25–200 °C, and axial displacement rates changed stepwise among 0.1, 1 and 10 μm/s.
Opal gouge showed frictional strength increasing with increasing T, rate-weakening behavior at T ≥ 100 °C, and stick slips at T ≥ 150 °C. When fitted by the rate- and state-dependent friction constitutive law, friction parameter a decreases while friction parameter b significantly increases with increasing T ≥ 100 °C, so that (a – b) value resultantly decreases to negative at T ≥ 100 °C. Microstructures of the opal gouge after the experiments at T ≥ 100 °C suggest the operation of pressure solution during those experiments. Thermally activated pressure solution possibly promoted healing of gouge particles to significantly increase b value with increasing T ≥ 100 °C, thereby decreasing (a – b) value to negative at T ≥ 100 °C. Our experimental results also suggest that seismogenic faulting at the Japan Trench subduction zone possibly occurs at depths where T ≥ 100 °C, provided that the plate boundary thrust is located within opaline chert on the subducting Pacific plate.
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号