Assessing the roles of wear and roughness on dynamic fault friction

评估磨损和粗糙度对动态故障摩擦的作用

• 批准号: 2338973
• 负责人: Monica Barbery
• 金额: $ 41.48万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-06-01 至 2027-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2338973&HistoricalAwards=false
• 关键词: Assessing; roles; wear; roughness; dynamic

Faults that host earthquakes are naturally rough. Rough patches on fault surfaces can collide and lock, preventing any further movement on a fault. Earthquakes begin when these rough patches break, and earthquake characteristics are controlled by frictional processes at the fault surface that evolve as the earthquake occurs. This project will advance our understanding of the physics of earthquakes by exploring two mechanisms that may regulate the friction of faults during earthquakes. The first occurs when heating leads to increased pressure in fluids, which can promote continued slip in earthquakes through lubrication, and the second is hardening due to producing more space for the lubricating fluids, which can impede earthquakes. To better understand these processes, the PI will conduct experiments at earthquake like conditions using a one-of-a-kind deformation apparatus at Brown University. The PI will test the roles of natural fault roughness and wear processes on the two competing processes. The results from this work will advance our understanding of earthquake physics and will inform the development and modification of new and existing earthquake rupture models. These models play a vital role in mitigating earthquake hazard and risk worldwide by improving the understanding of earthquake processes. This project will also enable the PI’s continued participation in DEEPS CORES, a program that develops and implements STEM curriculum for local Providence public schools. DEEPS CORES aims to expand participation in STEM fields from under-represented groups and to improve science literacy of the general public.Experimental validation of physics-based constitutive equations that describe the frictional behavior of geologic materials during seismic slip is a critical step in advancing physics-based dynamic rupture models for earthquakes. This work will use the newly modified Tullis Rotary Shear Apparatus at Brown University to conduct several suites of dynamic rock friction experiments investigating two mechanisms that may regulate the frictional behavior of faults during earthquakes: thermal pore-fluid pressurization weakening (TPW) and dilatancy hardening (DH). TPW occurs as frictionally heated pore fluids thermally expand faster than the fault pores. In poorly drained conditions during seismic slip, this leads to increases in the pore pressure that decrease the shear stress acting on the fault thereby weakening the fault. DH has the opposite effect in which shearing causes the formation of new microcracks increases total pore volume, thereby reducing pore fluid pressure and strengthening faults. TPW will only be significant during earthquakes if DH is minimal. To elucidate to roles of wear and fault roughness on dynamic friction and explore the balance between TPW and DH, the PI is conducting experiments at slip rates up to 1 m/s, elevated confining pressures (45-60 MPa), and elevated pore pressures (25-40 MPa) on samples with both variable permeability and sliding surface roughness mimicking the range of fault roughness measured on faults in nature. Mechanical data will be combined with microstructural analysis and micromechanical modelling to guide the analysis and interpretation of results. These experiments will be the first with independently controlled and elevated pore pressure, confining pressure, and normal stress at slip rates of 1 m/s. It will establish conditions under which wear processes, enhanced by natural fault roughness, allow TPW to develop in samples with varying permeabilities and will also establish the extent to which DH counteracts TPW on rough surfaces at high displacements.This project is jointly funded by the Division of Earth Sciences, Geophysics Program and the Established Program to Stimulate Competitive Research (EPSCoR).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.

引发地震的断层自然是粗糙的。断层表面的粗糙斑块可能会碰撞并锁定，从而阻止断层上的任何进一步移动。当这些粗糙的斑块破裂时，地震就开始了，地震的特征是由地震发生时断层表面的摩擦过程控制的。这个项目将通过探索地震中可能调节断层摩擦的两种机制来推进我们对地震物理的理解。第一种是加热导致流体压力增加，这可以通过润滑促进地震中的持续滑动，第二种是硬化，因为为润滑流体提供了更多的空间，这可以阻止地震。为了更好地理解这些过程，PI将在类似地震的条件下进行实验，使用布朗大学的一种独一无二的变形设备。PI将测试自然断层粗糙度和磨损过程在两个相互竞争的过程中的作用。这项工作的结果将促进我们对地震物理学的理解，并将为新的和现有的地震破裂模型的发展和修改提供信息。这些模型通过提高对地震过程的认识，在减轻世界范围内的地震灾害和风险方面发挥着至关重要的作用。该项目还将使PI继续参与DEEPS CORES，这是一个为当地普罗维登斯公立学校开发和实施STEM课程的项目。deepcores旨在扩大代表性不足群体对STEM领域的参与，并提高公众的科学素养。实验验证描述地震滑动过程中地质材料摩擦行为的基于物理的本构方程是推进基于物理的地震动态破裂模型的关键一步。这项工作将使用布朗大学新改进的Tullis旋转剪切仪进行几组动态岩石摩擦实验，研究地震中可能调节断层摩擦行为的两种机制：热孔隙流体加压减弱（TPW）和膨胀硬化（DH）。TPW的发生是由于摩擦加热的孔隙流体比断层孔隙热膨胀得快。在地震滑动时排水不良的条件下，孔隙压力增加，从而降低作用在断层上的剪应力，从而削弱断层。DH则相反，剪切作用导致新的微裂缝形成，增加总孔隙体积，从而降低孔隙流体压力，强化断层。只有在震源差最小的情况下，TPW才会有意义。为了阐明磨损和断层粗糙度对动摩擦的作用，并探索TPW和DH之间的平衡，PI在具有可变渗透率和滑动表面粗糙度的样品上进行了高达1 m/s、提高围压（45-60 MPa）和提高孔隙压力（25-40 MPa）的实验，模拟了在自然断层上测量的断层粗糙度范围。力学数据将与微观结构分析和微观力学建模相结合，以指导结果的分析和解释。这些实验将是第一次在1 m/s滑移速率下独立控制和提高孔隙压力、围压和正应力的实验。它将建立由自然断层粗糙度增强的磨损过程的条件，允许TPW在具有不同渗透率的样品中发展，并且还将确定在高排量下粗糙表面上DH抵消TPW的程度。该项目由地球科学部、地球物理计划和促进竞争研究的既定计划（EPSCoR）共同资助。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。