Abstract New insights into the pressure and temperature conditions on fault surfaces during seismic slip are provided by Raman-active vibrational modes of SiO2 glass. We performed triaxial stick-slip experiments at room temperature and high normal stresses on pre-ground, high-purity silica glass surfaces. During slip, velocities exceed 0.32 m s−1 over durations of less than one millisecond, generating frictional heat and locally melting the fault surfaces. Temperature increases permit structural rearrangement within the melt; these changes are preserved by rapid quenching. Using Raman spectroscopy, we analyse melt-welded regions and show that these areas exhibit systematic changes in the spectra of silica. Changes result from a decrease in the inter-tetrahedral Si-O-Si bond angle and are correlated to increasing silica glass density in the slip regions. Densification results from both rapid cooling rates and exposure to very high pressures at asperity contacts. We use data from other experiments to calibrate these effects, estimating quench temperatures up to 1800 K and pressures of ∼180 MPa. These results provide the first quantitative evidence for the effects of quench rates and high inter-asperity pressures on the physics of melting and quenching during seismic slip and its impact on fault behaviour.

中文翻译：

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地震滑动过程中断层凹凸的动态压力和温度条件的量化

摘要 SiO2 玻璃的拉曼主动振动模式为地震滑动期间断层表面的压力和温度条件提供了新的见解。我们在室温和高法向应力下在预先研磨的高纯度石英玻璃表面上进行了三轴粘滑实验。在滑动过程中，速度在不到 1 毫秒的持续时间内超过 0.32 m s-1，产生摩擦热并局部熔化断层表面。温度升高允许熔体内的结构重排；这些变化通过快速淬火得以保留。我们使用拉曼光谱分析了熔焊区域，并表明这些区域在二氧化硅光谱中表现出系统性变化。变化是由四面体间 Si-O-Si 键角的减小引起的，并且与滑移区域中二氧化硅玻璃密度的增加有关。致密化是由快速冷却速率和在粗糙接触处暴露于非常高的压力造成的。我们使用来自其他实验的数据来校准这些影响，估计淬火温度高达 1800 K，压力约为 180 MPa。这些结果为地震滑动期间淬火速率和高粗糙度间压力对熔化和淬火物理的影响及其对断层行为的影响提供了第一个定量证据。