Laboratory studies suggest that seismogenic rupture on faults in carbonate terrains can be explained by a transition from high friction, at low sliding velocities (V), to low friction due to rapid dynamic weakening as seismic slip velocities are approached. However, consensus on the controlling physical processes is lacking. We previously proposed a microphysically based model (the “Chen–Niemeijer–Spiers” [CNS] model) that accounts for the (rate‐and‐state) frictional behavior of carbonate fault gouges seen at low velocities characteristic of rupture nucleation. In the present study, we extend the CNS model to high velocities (1 mm/s ≤ V ≤ 10 m/s) by introducing multiple grain‐scale deformation mechanisms activated by frictional heating. As velocity and hence temperature increase, the model predicts a continuous transition in dominant deformation mechanisms, from frictional granular flow with partial accommodation by plasticity at low velocities and temperatures, to grain boundary sliding with increasing accommodation by solid‐state diffusion at high velocities and temperatures. Assuming that slip occurs in a localized shear band, within which grain size decreases with increasing velocity, the model results capture the main mechanical trends seen in high‐velocity friction experiments on room‐dry calcite‐rich rocks, including steady‐state and transient aspects, with reasonable quantitative agreement and without the need to invoke thermal decomposition or fluid pressurization effects. The extended CNS model covers the full spectrum of slip velocities from earthquake nucleation to seismic slip rates. Since it is based on realistic fault structure, measurable microstructural state variables, and established deformation mechanisms, it may offer an improved basis for extrapolating lab‐derived friction data to natural fault conditions.

中文翻译：

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整个地震周期滑动速率下碳酸盐断层摩擦的微物理模拟


实验室研究表明，碳酸盐岩地形断层上的震源破裂可以通过从低滑动速度（ V ）下的高摩擦过渡到由于接近地震滑动速度时动态迅速减弱而导致的低摩擦。然而，对于控制物理过程缺乏共识。我们之前提出了一个基于微观物理的模型（“Chen-Niemeijer-Spiers”[CNS]模型），该模型解释了在破裂成核的低速特征下看到的碳酸盐断层泥的（速率和状态）摩擦行为。在本研究中，我们通过引入摩擦加热激活的多种晶粒尺度变形机制，将 CNS 模型扩展到高速（1 mm/s ≤ V ≤ 10 m/s）。随着速度和温度的增加，该模型预测主要变形机制会持续转变，从低速和低温下塑性部分调节的摩擦颗粒流，到高速和高温下固态扩散增加调节的晶界滑动。假设滑移发生在局部剪切带中，其中晶粒尺寸随着速度的增加而减小，模型结果捕获了在室内干燥的富含方解石的岩石的高速摩擦实验中看到的主要力学趋势，包括稳态和瞬态方面，具有合理的定量一致性，并且不需要调用热分解或流体加压效应。扩展的 CNS 模型涵盖了从地震成核到地震滑移速率的整个滑移速度范围。 由于它基于真实的断层结构、可测量的微观结构状态变量和已建立的变形机制，因此它可以为将实验室得出的摩擦数据外推到自然断层条件提供改进的基础。