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首页> 外文期刊>Tectonophysics: International Journal of Geotectonics and the Geology and Physics of the Interior of the Earth >Influence of subduction zone conditions and gouge composition on frictional slip stability of megathrust faults
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Influence of subduction zone conditions and gouge composition on frictional slip stability of megathrust faults

机译：俯冲带条件和切屑组成对大推力断层摩擦滑动稳定性的影响

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摘要

To understand the temperature/depth distribution of destructive earthquakes in subduction megathrusts, and the mechanisms of nucleation of these events, data on the frictional behaviour of phyllosilicate/quartz-rich megathrust fault gouges under in-situ conditions are needed. We performed rotary shear friction experiments at effective normal stresses of 25-200. MPa, pore fluid pressures of 50-200. MPa, at 140-600. °C and sliding velocities of 1-100. μm/s, using gouge mixtures with an illite:quartz ratio between 65:35 and zero. Experiments on 65:35 mixtures, deformed at an effective normal stress (. σ_n ~(eff)) of 170. MPa, a pore fluid pressure (. P_f) of 100. MPa and 150-500. °C provided a reference dataset. This showed three temperature-dependent slip stability regimes with potentially unstable, velocity-weakening behaviour at 250-400. °C and velocity-strengthening at lower and higher temperatures. The velocity-weakening regime was found to shift towards higher temperatures with decreasing σ_n ~(eff), being located at ~~. 350-600. °C at 50. MPa. Increasing quartz content and decreasing sliding velocity also displaced the velocity-weakening regime towards lower temperatures. Increasing P_f increased (. a-b) at all temperatures, narrowing the temperature extent of the velocity-weakening regime. We explain our results qualitatively in terms of a microphysical model in which changes in friction coefficient and (. a-b) with velocity and temperature are brought about by changes in the relative importance of deformation of the clast phase, by thermally activated stress corrosion cracking and pressure solution, versus athermal granular flow of the mixture accompanied by dilatation. Our results imply that the depth extent of the seismogenic zone on subduction megathrusts depends not only on temperature and that to predict its location, it is essential to have well-constrained depth profiles for pore fluid pressure and effective normal stress.
机译：为了了解俯冲巨推力破坏性地震的温度/深度分布，以及这些事件的成核机理，需要有关层状硅酸盐/富含石英的巨推力断层泥在原位条件下的摩擦行为数据。我们在有效法向应力为25-200的条件下进行了旋转剪切摩擦实验。 MPa，孔隙流体压力为50-200。 MPa，在140-600。 °C和1-100的滑动速度。 μm/ s，使用伊利石：石英比率为65:35到零之间的切碎混合物。在65:35的混合物上进行的实验，在170. MPa的有效法向应力（。σ_n〜（eff）），100。MPa的孔隙流体压力（。P_f）和150-500的压力下变形。 °C提供了参考数据集。这显示了三种与温度有关的滑移稳定性状态，在250-400时具有潜在的不稳定，速度减弱行为。 °C和更高和更低温度下的速度强化。发现速度弱化状态随着σ_n〜（eff）的减小而朝着更高的温度移动，位于处。 350-600。在50. MPa下的温度。石英含量的增加和滑动速度的降低也使速度减弱状态趋向于较低的温度。在所有温度下P_f的增加都会增加（.a-b），从而使速度减弱状态的温度范围变窄。我们用微观模型定性地解释了我们的结果，在该模型中，摩擦系数和（.ab）随速度和温度的变化是由裂变相变形的相对重要性的变化，热活化应力腐蚀开裂和压力引起的。溶液，相对于混合物伴随膨胀的无热颗粒流。我们的结果表明，俯冲超大推力上的地震成因带的深度范围不仅取决于温度，而且要预测其位置，对于孔隙流体压力和有效法向应力而言，具有严格约束的深度剖面至关重要。

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