Collaborative Research: The rheological behavior of gouge at high temperature

大地震是沿着地球构造板块的断层产生的，因为岩石相互剪切。评估与断层带相关的危险需要了解促进地震成核的条件。断层上的剪切可以以不稳定的方式发生，其中快速滑动允许地震成核，或者以稳定的方式发生，其中滑动稳定并抑制地震成核。尽管人们已经做了大量的工作来了解在地壳相对寒冷的部分导致地震成核的条件，但在热地区断层的稳定性方面，人们的认识仍然存在相当大的差距。这些较热的地区包括火山爆发的管道和海洋中的变形断层。我们的工作将确定温度对断层稳定性的影响，以便准确评估这些地区的危害和风险。这项工作还将为博士后、研究生和本科阶段的早期职业研究人员提供培训。参与这项研究的团队还将通过国际会议向在科学领域代表性不足的群体介绍高温实验岩石物理学，他们将开设一个关于地震和断层的短期课程，以面对面和虚拟的形式提供给世界各地的早期职业研究人员。我们将具体回答与高温下故障稳定性有关的三个问题。首先，极端温度如何影响断层材料的强度和稳定性？为了回答这个问题，我们将在广泛的条件下对断层材料进行变形实验。第二，是什么微观机制控制着断层材料的强度，它们又是如何相互竞争的？为了回答这个问题，我们将使用高分辨率显微镜将力学测量结果与基于岩石变形微物理的理论模型进行比较。第三，这些机制如何相互作用以确定断层的稳定性，这对自然环境下地震的深度范围意味着什么？为了回答这个问题，我们将评估微观特征、宏观强度、观察到的稳定性和变形率之间的关系。这些观测的最终结果将是一个关于高温下断裂带稳定性的精细模型，然后我们将把它与相对“热”地区现有的地震地点目录进行比较，以检验我们对地震成核深度范围的预测。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Major earthquakes are generated along faults in Earth’s tectonic plates as rocks are sheared past each other. Assessing the hazard associated with a fault zone requires understanding the conditions that promote earthquake nucleation. Shearing on faults can occur in an unstable manner, where rapid slip allows an earthquake to nucleate, or in a stable manner, where slip is steady and suppresses earthquake nucleation. Although much work has been devoted to understanding the conditions that lead to earthquake nucleation in the relatively cold portions of Earth’s crust, there is still a considerable gap in knowledge regarding the stability of faults in hotter regions. These hotter regions include the conduits of explosive volcanoes and transform faults in the oceans. Our work will determine the influence of temperature on fault stability to enable accurate assessments of hazard and risk in these regions. This work will also provide training to early-career researchers at the postdoctoral, graduate, and undergraduate levels. The team involved in this research will also work to introduce high-temperature experimental rock physics to groups typically underrepresented in the sciences via international conferences, and they will run a short-course on earthquakes and faulting to be offered to early-career researchers around the world in an in-person and virtual format.We will specifically answer three questions related to fault stability at high temperatures. First, how do extreme temperatures affect the strength and stability of fault materials? To answer this question, we will conduct deformation experiments on fault materials over a wide range of conditions. Second, what microscopic mechanisms control the strength of fault materials, and how do they compete with one another? To answer this question, we will use high-resolution microscopy to compare mechanical measurements with theoretical models based on the microphysics of rock deformation. Third, how do these mechanisms interact to determine fault stability, and what does this mean for the depth range of earthquakes in natural settings? To answer this question, we will assess the relationships among microscopic features, the macroscopic strength, the observed stability, and the rate of deformation. The net result of these observations will be a refined model for the stability of fault zones at high temperatures, which we will then compare to available catalogs of earthquake locations in relatively “hot” regions to test our predictions of the depth range of earthquake nucleation.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.