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.

引发地震的断层本质上是粗糙的，断层表面上的粗糙斑块会发生碰撞和锁定，当这些粗糙的斑块破裂时，就会阻止地震的发生，而地震特征是由断层表面随断层表面的摩擦过程控制的。该项目将通过探索两种可能调节地震期间断层摩擦的机制来增进我们对地震物理学的理解。第一种机制发生在加热导致流体压力增加时，这可以通过润滑促进地震中的持续滑动，和第二个是由于为润滑液产生更多空间而硬化，这可以阻止地震。为了更好地了解这些过程，PI 将使用布朗大学的一种独一无二的变形装置在类似地震的条件下进行实验。将测试自然断层粗糙度和磨损过程在两个竞争过程中的作用，这项工作的结果将增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开发和修改提供信息。在该项目还将使 PI 能够继续参与 DEEPS CORES，该项目为当地普罗维登斯公立学校开发和实施 STEM 课程，旨在扩大 STEM 领域的参与。描述地震滑移过程中地质材料摩擦行为的基于物理的本构方程的实验验证是推进的关键一步这项工作将使用布朗大学新改进的塔利斯旋转剪切装置进行几套动态岩石摩擦实验，研究可能调节地震期间断层摩擦行为的两种机制：热孔隙流体在地震滑移期间，由于摩擦加热的孔隙流体的热膨胀速度快于断层孔隙，因此会发生加压弱化（TPW）和剪胀硬化（DH）。这导致孔隙压力增加，从而减少作用在断层上的剪切应力，从而削弱断层，而DH具有相反的作用，其中剪切导致新微裂缝的形成，增加总孔隙体积，从而降低孔隙流体压力并强化断层。只有当 DH 最小时，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 正在进行滑移率高达 1 的实验。 m/s、升高的围压（45-60 MPa）和升高的孔隙压力（25-40 MPa），具有可变渗透率和滑动表面粗糙度的样品将模拟在自然界断层上测量的断层粗糙度范围。结合微观结构分析和微观力学建模来指导结果的分析和解释，这些实验将是第一个在滑移速率下独立控制和升高的孔隙压力、围压和正应力的实验。 1 m/s 它将建立由自然断层粗糙度增强的磨损过程允许 TPW 在具有不同渗透率的样品中形成的条件，并将确定 DH 在高位移下在粗糙表面上抵消 TPW 的程度。该奖项由地球科学部、地球物理学计划和刺激竞争性研究既定计划 (EPSCoR) 联合资助。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准。