Investigating dynamic friction using earthquake ruptures produced in the laboratory

这项研究将通过在实验室中进行小型地震来推进对动态摩擦定律的基本理解。动态摩擦在地震破裂如何沿着沿着地壳中预先存在的断层（如加州的圣安德烈亚斯断层）传播并释放引起破坏性震动的波方面起着关键作用。然而，动摩擦的基本结构和演化仍然是地震科学中的主要不确定性之一。这项研究将提高我们对动摩擦的理解，从而提高对震源物理的理解。通过改进地震断层的摩擦力公式，本研究致力于为动态破裂模拟和基于物理的地震危险性评估提供关键要素。本研究将使用实验室实验研究动态摩擦力，其特征是动态破裂沿着摩擦界面自发传播。研究人员将采用数字图像相关技术与高速摄影相结合，以真实的表征位移，速度和应力以及破裂界面摩擦力的全场演变。在某些实验中，在样品的界面上添加岩石泥#8232;将进一步增加该装置与地震问题的相关性。此外，计划研究摩擦演变的位置，在那里的故障满足一个自由表面和故障的正应力变化迅速，显着，将允许测试最近的想法剪切阻力不成正比的快速变化的正应力，而是演变成这样的比例与滑动。这项工作还将通过进行流体注入实验和研究注入触发动态事件的机制来探索流体在断层中的作用。所获得的摩擦数据将有助于评估和改进现有的动态摩擦公式，通过引入适当的新物理在现有的形式主义，甚至建议新的和改进的动态摩擦定律。推导出的摩擦公式将通过我们的实验装置的正向模拟进行验证。

This research that will advances fundamental understanding of dynamic friction laws by performing mini-earthquakes in the laboratory. Dynamic friction plays a pivotal role in how earthquake ruptures propagate along pre-existing faults in the Earth's crust, such as the San Andreas Fault in California, and release waves that cause destructive shaking. Yet, the fundamental structure and evolution of dynamic friction is still one of the main uncertainties in earthquake science. The proposed study will enhance our understanding of dynamic friction and hence of earthquake source physics. By improving friction formulations for earthquake-producing faults, this study strives to produce a key ingredient for dynamic rupture simulations and physics-based assessment of seismic hazard.The study will investigate dynamic friction using laboratory experiments, featuring dynamic ruptures spontaneously propagating along a frictional interface. The researchers will employ a digital image correlation technique in combination with high-speed photography to characterize in real time the full-field evolution of displacements, velocities, and stresses, and of friction along rupturing interfaces. The addition of rock gouge
to the interface of the samples in some experiments will further increase the relevance of the setup to earthquake problems. Furthermore, plans to study friction evolution at locations where a fault meets a free surface and where fault-normal stresses vary rapidly and significantly, will allow tests for recent ideas of shear resistance not being directly proportional to rapid variations in normal stress but rather evolving to such proportionality with slip. The work will also explore the effect of fluids in faulting by conducting
experiments with fluid injection and studying the regime in which the injection triggers dynamic events. The obtained friction data will help to evaluate and improve the existing dynamic friction formulations by introducing the appropriate new physics in to existing formalisms and by even suggesting new and improved dynamic frictional laws. The inferred friction formulations will be verified by forward simulations of our experimental setup.