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

摩擦特性和材料特性沿构造断层变化，直接影响地震的孕育、传播和止震。天然断层的这种异质性使地震变得复杂和难以预测。一些断层段大多是锁定的，但经常发生地震。其他地区正在缓慢增长，总体上是稳定的。然而，在知之甚少的情况下，在不稳定区段孕育的地震可能会传播到稳定的断层区段，并导致特别大和破坏性的事件。该项目通过大规模实验室地震实验和基于物理的数值模拟相结合的方法来研究导致蠕动断层段激活的原因。模拟的断层由稳定和不稳定部分组成，真实地再现了非均质断层上地震的机制。更好地了解稳定和不稳定断层段之间的相互作用将有助于我们评估极大地震的可能性，这可能会增强现有的地震危险性评估工具。这个项目对社会是有益的，因为它将帮助我们更好地了解地震并开发评估这些危险的工具，它将增加对学生的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，旨在研究地震破裂阻止的机制，重点是不同的断层属性。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，而建模则提高了对实验结果的理解、推广和放大。大型实验室地震实验是在一台双轴机器上进行的，该机器产生了包含在3米长的花岗岩样品中的动态破裂事件的可重复序列。断层表面覆盖有断层泥，以生成速度减弱和速度增强的材料的斑块。为了探索结垢效应，在0.76m的台式双轴机上进行了额外的实验，使用塑料试件作为强迫块。较小规模的双直接剪切实验将以断层泥材料的摩擦本构参数为基准，这是解释更大规模的实验室地震观测和开发现实的、高分辨率的动态破裂和滞留数值模型的关键步骤。这些模拟包括一系列滑动事件，它们定量地再现了实验的相关规模，包括仪器的实际尺寸和破裂过程区域。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.