Collaborative Research: Mechanics of Earthquake Fault Zones: Particle Dynamics Simulations and Laboratory Experiments

协作研究：地震断裂带的力学：粒子动力学模拟和实验室实验项目摘要实验室研究对我们理解地震成核、动态破裂和剪切变形做出了重大贡献，然而，这些实验的结果往往很难扩大到自然断层系统。以粒子为基础的数值模型，成功地再现了广泛的实验室和自然现象，可能会有所帮助。这一合作研究项目旨在(A)改进和完善现有的基于粒子的数值技术，以更好地复制实验室实验结果，特别是摩擦强度和滑动稳定性的一阶和二阶变化，以及(2)弥合这些改进的模型和自然断层之间的差距，从而能够研究复杂构造断层的结构演化。实验和数值结果正在进行比较，以指导粒子间数值接触定律的更新，以更好地再现真实的物理化学表面相互作用。主要的焦点是在两组实验中准确地约束滑动摩擦系数的基准值(“拜尔利定律”)，以及它随剪切、膨胀和压实的变化。重点还将包括摩擦随接触时间和滑动速度的二阶变化，即与速率和状态相关的摩擦。数值模型进一步有助于分离不同边界条件下作用于断裂带内的变形机制，包括剪切局部化、晶界滑动、颗粒滚动、平移和断裂。这项工作的结果将对理解断层力学和地震物理，包括断层相互作用、地震触发和地震危险性评估产生重大影响。

Collaborative Research: Mechanics of Earthquake Fault Zones:Particle Dynamics Simulations and Laboratory ExperimentsPROJECT ABSTRACTLaboratory studies have contributed significantly to our understanding of earthquake nucleation, dynamic rupture, and shear deformation, however, results of these experiments are often difficult to scale up to natural fault systems. Particle-based numerical models, which have successfully reproduced a wide-range of observed laboratory and natural phenomena, can help. This collaborative research project is designed to (a) improve and refine existing particle-based numerical techniques to better replicate laboratory experimental results, in particular, first and second order variations in frictional strength and sliding stability, and (2) bridge the gap between these improved models and natural faults, allowing investigation of the structural evolution of complex tectonic faultsThis research involves parallel laboratory and numerical experiments, conducted under a wide range of identical initial and boundary conditions. The experimental and numerical results are being compared, guiding updates of the numerical interparticle contact laws to better reproduce realistic physico-chemical surface interactions. The primary focus is on accurately constraining the base ("Byerlee's Law") coefficient of sliding friction in the two sets of experiments, as well as its variation with shear, dilation, and compaction. Focus will also include the 2nd-order variations in friction with contact time and slip velocity, i.e., rate- and state-dependent friction. The numerical models further help to isolate the deformation mechanisms acting within the fault zones under different boundary conditions, including shear localization, grain-boundary sliding, particle rolling, translation, and fracture. Results of the proposed work will have significant impact on understanding fault mechanics and earthquake physics including fault interaction, earthquake triggering, and seismic hazard assessment.