CAREER: Combining physical and numerical modes to characterize the contribution of semi-brittle rheology to deformation dynamics and strain transients.

构造断层是地壳中容纳构造板块缓慢运动的裂缝。当断层长时间蠕动时，断层周围积累的应力可以缓慢释放。这种粘性行为被称为无地震，因为它不会产生地震。断层也可能因脆性破坏而突然滑动。大多数构造断层表现出粘性(无地震)和脆性(地震)两种行为。了解断层行为是如何相互作用的，对于解释地震和改进危险预测至关重要。然而，这项任务具有挑战性，因为这些行为发生在非常不同的时间尺度上。在这里，研究人员使用实验和数值模拟来解释断层动力学。它们使用粘性和脆性材料的独特组合，这些材料混合在一起，表现得像断层。通过使混合物变形，他们确定了产生缓慢变形和突然滑移的因素。通过建模，他们将其结果应用于自然系统，并解释了故障的行为。该项目对地震危险性预测具有很强的影响。它为一名职业生涯早期的女科学家、一名博士后助理和一名研究生提供支持。它为本科生和高中生提供培训机会。此外，它还促进了科学传播课教材的开发。其目的是提高学生的科学方法论意识，并加强他们向广大受众传达结果的能力。这项为期五年的奖项由极端事件预测和抵御计划(PREEVENTS)共同资助。半脆性材料涵盖与破裂事件(地震)有关的短时间尺度，以及与粘性流动(韧性地壳)有关的更长时间尺度。它们的行为范围可以潜在地解释所观察到的各种断层动力学。然而，关于半脆性材料的流变学的现有数据有限，关于在存在流体的情况下涉及颗粒粉碎的材料的数据更少，例如在断层泥中可能发生的情况。在这里，研究人员使用粘性Carbopol和脆性水凝胶球体的混合物，这种球体表现出构造断层运动背后的半脆性行为。样品在一种新的最先进的设备中进行剪切，该设备允许成像流体流动、颗粒运动和粉碎。该团队系统地研究了颗粒粉碎对滑移动力学、脆性和粘性材料之间的分布、法向力、总应变和粘度的影响。实验结果被输入到一个数值模型中，该模型捕获了地质时间尺度上的地球材料的物理特性。模型结果探索了参数空间以及半脆性变形是否会导致稳定蠕变和粘滑断层运动之间的连续体。这一奖项反映了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。

Tectonics faults are cracks in the Earth's crust accommodating the slow motions of tectonics plates. The stress accumulated around faults can be released slowly when faults creep over long periods of time. This viscous behavior is called aseismic because it does not produce earthquakes. Faults can also slip abruptly by brittle failure. Most tectonics faults exhibit both viscous (no earthquake) and brittle (earthquakes) behaviors. Understanding how fault behaviors interplay is critical to explain earthquakes and improve hazard forecasting. This task is, however, challenging because these behaviors occur on very different time scales. Here, the researchers use experiments and numerical modeling to explain fault dynamics. They use a unique combination of viscous and brittle materials which, mixed together, behave like faults. By deforming the mixture, they identify the factors producing slow deformation and abrupt slip. Using modeling, they apply their results to natural systems and explain the behaviors of fault. The project has strong implications for earthquake hazard forecasting. It provides support to an early-career female scientist, a postdoctoral associate and a graduate student. It offers training opportunities to undergraduate and high-school students. Furthermore, it fosters the development of teaching materials for a science communication class. The goal is to increase students' awareness of scientific methodology and strengthen their ability to communicate their results to a broad audience. This five-year award is co-funded by the Prediction of and Resilience against Extreme Events (PREEVENTS) program.Semi-brittle materials cover short time scales associated with rupture events (earthquakes) and much longer ones associated with viscous flow (ductile crust). Their range of behaviors can potentially explain the observed various fault dynamics. Yet, there is limited data available on the rheology of semi-brittle materials; and even less on materials involving grain comminution in the presence of fluids, as can occur in fault gouges. Here, the researchers use a mixture of viscous Carbopol and brittle hydro-gel spheres, which exhibits the semi-brittle behaviors underlying tectonic fault motions. Specimens are sheared in a new state-of-the-art apparatus which allows imaging fluid-flow, and particle motions and comminution. The team systematically investigates the effects on slip dynamics of grain comminution, distribution between brittle and viscous materials, normal force, total strain and viscosity. Experimental results are input into a numerical modeling which captures the physics of Earth materials on geological time scales. The model outcomes explore the parameter space and whether semi-brittle deformation can lead to the continuum between steady creep and stick-slip fault motions.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.