Collaborative Research: Investigating the interplay between creeping and seismogenic fault sections using large-scale laboratory experiments and high-resolution numerical models

构造断层的构造和物质性质沿着方向变化，直接影响地震的孕育、传播和停止。天然断层的这种不均匀性使得地震变得复杂和难以预测。一些断层部分大多被锁定，但经常发生地震。其他部分蠕动，总体稳定。然而，在不太了解的情况下，在不稳定部分中成核的地震可以传播到稳定断层部分，并导致特别大的破坏性事件。本研究将实验室大规模地震实验与物理数值模拟相结合，探讨蠕动断层段活动的原因。模拟断层由稳定和不稳定部分组成，真实地再现了非均匀断层地震的力学机制。更好地了解稳定和不稳定断层之间的相互作用将有助于我们评估发生特大地震的可能性，这可能会增强现有的地震危险性评估工具。该项目对社会有益，因为它将帮助我们更好地了解地震并开发评估这些危害的工具，它将增加学生的STEM教育，同时支持地震研究的新研究人员。这项研究是一项合作努力，以调查地震破裂制动的力学，重点是异质断层属性。它结合了多尺度实验室实验和数值模拟。实验为数值模型提供了物理约束，而建模提高了对实验结果的理解、概括和放大。大规模的实验室地震实验进行双轴机，产生可重复序列的动态破裂事件包含在一个3米长的花岗岩样品。断层表面覆盖着断层泥，以产生速度减弱和速度加强材料的斑块。为了探索缩放效应，额外的实验进行了0.76米的桌面双轴机使用塑料样品作为施力块。小规模的双直剪实验将基准的断层泥材料的摩擦本构参数，一个重要的步骤，解释大规模的实验室地震观测和发展现实的，高分辨率的动态破裂和逮捕的数值模型。模拟包括滑动事件的序列，定量再现实验的相关规模，包括设备的实际尺寸和破裂过程区。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Frictional and material properties vary along tectonic faults and directly affect the nucleation, propagation and arrest of earthquakes. This heterogeneous character of natural faults is what makes earthquakes complex and difficult to predict. Some fault sections are mostly locked but recurrently host earthquakes. Other sections are creeping and generally stable. However, under poorly understood circumstances, earthquakes that nucleated in an unstable section can propagate far into stable fault sections and result in particularly large and destructive events. This project investigates the causes that lead to activation of the creeping fault sections by combining large-scale laboratory earthquake experiments with physics-based numerical simulations. The modeled fault consists of stable and unstable parts which realistically reproduce the mechanics of earthquakes at heterogeneous faults. A better understanding of the interaction between stable and unstable fault sections will help us evaluate the potential for extremely large earthquakes that will likely enhance existing seismic hazard assessment tools. This project is a benefit to society because it will help us to better understand earthquakes and develop tools to assess these hazards, and it will add to STEM education of students while supporting new researchers in earthquake studies.This research is a collaborative effort to investigate the mechanics of earthquake rupture arrest with focus on heterogeneous fault properties. It combines multiscale laboratory experiments and numerical modeling. The experiments provide physical constraints for the numerical models, while the modeling improves understanding, generalizing, and scaling up the experimental results. Large-scale laboratory earthquake experiments are conducted on a biaxial machine that generates repeatable sequences of dynamic rupture events contained within a 3-m long granite sample. The fault surfaces are coated with gouge to generate patches of velocity-weakening and velocity-strengthening materials. To explore scaling effects, additional experiments are conducted on a 0.76 m tabletop biaxial machine using plastic samples as forcing blocks. Smaller-scale double-direct shear experiments will benchmark the frictional constitutive parameters of the gouge materials, an essential step for the interpretation of the larger-scale laboratory earthquake observations and the development of realistic, high-resolution numerical models of dynamic rupture and arrest. The simulations include sequences of slip events that quantitatively reproduce the relevant scales of the experiments including the actual size of the apparatus and the rupture process zone.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.