EAR PF: Investigating the competition between thermal pressurization and dilatancy on rough surfaces at earthquake slip rates

该奖项全部或部分由《2021年美国救援计划法案》(Public Law 117-2)资助。NSF EAR博士后奖学金授予莫妮卡·巴贝里博士，在特里·图利斯博士的指导下，他将在布朗大学研究地震物理。巴贝里博士将致力于了解岩石在断层上快速运动时产生的摩擦力下的表现。博士后研究员将使用新的实验机械在真实地震的速度和压力下进行第一次岩石摩擦实验，以了解地震过程和相关风险。这项工作将提高现有实验室结果与自然相适应的能力。这项研究将有助于开发和修改新的和现有的地震模型，这些模型在减轻地震风险方面发挥着至关重要的作用。除了这些研究活动，巴贝里博士还将与普罗维登斯公立学校合作，为布朗大学的一项教育推广计划制定和实施课程，并将在地球、环境和行星科学系内共同教授一门研究生和本科生课程。热孔隙流体加压(TP)的动态减弱和膨胀硬化(DH)的动态强化是地震期间断层摩擦强度和稳定性的理论机制。当摩擦加热的孔隙流体沿着不排水的断层膨胀以摩擦削弱断层时，TP就会发生。在剪切过程中，由于微裂缝的发展，以及先前配对的断层表面因滑动而变得不匹配，这两种情况都增加了孔隙空间，并摩擦加强了断层，从而发生了差错。这两个过程都与滑动面的粗糙度和位移历史密切相关，然而，只有当Dh最小时，Tp才会对导致地震不稳定的摩擦减弱做出显着贡献。利用一种新改进的旋转剪切仪进行岩石摩擦实验，以考察TP和DH在高滑移率(≥100 mm/S)、高围压(≥25 Mpa)和高孔压(≥25 Mpa)条件下的有效性。实验结果将与建模相结合，以表征在一系列滑移率、粗糙度和位移尺度上TP和DH之间的竞争，以更好地了解如何将DH和TP过程扩展到天然断层上的地震。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).An NSF EAR Postdoctoral Fellowship has been awarded to Dr. Monica Barbery to investigate earthquake physics at Brown University under the mentorship of Dr. Terry Tullis. Dr. Barbery will work to understand how rocks behave when exposed to the friction produced when there is rapid movement on a fault. The postdoctoral fellow will use new experimental machinery to conduct the first rock friction experiments at the velocity and pressures of real earthquakes to understand earthquake processes and the associated risks. This work will improve the ability to scale existing laboratory results to nature. This research will help in the development and modification of new and existing earthquake models that play a vital role in mitigating earthquake risk. In addition to these research activities, Dr. Barbery will work with Providence public schools to develop and implement curriculum for an educational outreach program at Brown University and will co-teach a stacked graduate and undergraduate course within the Department of Earth, Environmental, and Planetary Sciences.Dynamic weakening by thermal pore fluid pressurization (TP) and dynamic strengthening by dilatancy hardening (DH) are mechanisms theorized to contribute to the frictional strength and stability of faults during earthquakes. TP occurs as frictionally heated pore fluids expand along undrained faults to frictionally weaken the fault. DH occurs as microcracks develop during shearing and as previously mated fault surfaces become unmated with slip, both of which increase pore space and frictionally strengthen the fault. Both processes are closely tied to the roughness and displacement history of the sliding surface however TP will only contribute significantly to the frictional weakening that leads to earthquake instability if DH is minimal. Rock friction experiments will be conducted to examine the efficacy of TP and DH at elevated slip rates (≥100 mm/s), elevated confining pressure (≥25 MPa), and elevated pore pressure (≥25 MPa) using a newly modified rotary shear apparatus. Experiment results will be combined with modelling to characterize the competition between TP and DH across a range of slip rate, roughness, and displacement scales to better understand how to scale DH and TP processes to earthquakes on natural faults.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.