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.

寄宿地震的断层自然是粗糙的。故障表面上的粗糙斑块可能会发生碰撞和锁定，从而阻止了故障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，而地震特征则由地震表面的摩擦过程控制，随着地震的发生而发展。该项目将通过探索可能调节地震期间断层摩擦的两种机制来提高我们对地震物理的理解。第一次发生加热会导致烟道压力增加，这可以通过润滑促进地震持续滑动，而第二个可以促进润滑液的空间，这可能会阻碍地震。为了更好地理解这些过程，PI将使用布朗大学使用一种独一无二的变形设备进行地震的实验。 PI将测试自然断层粗糙度的作用，并在两个竞争过程中磨损过程。这项工作的结果将提高我们对地震物理的理解，并将为新的和现有地震破裂模型的发展和修改提供信息。这些模型通过改善对地震过程的理解来减轻地震危害和风险，在减轻地震危害和风险中起着至关重要的作用。该项目还将使PI继续参与Deeps Cores，该计划为当地Providence公立学校开发和实施STEM课程的计划。深层核心旨在从代表性不足的群体中扩大参与STEM领域的参与并提高公众的科学素养。对基于物理学的组成型方程进行了实验验证，这些方程描述了塞斯维克滑移期间地质材料在基于地震的动态破裂模型的关键步骤。这项工作将使用布朗大学的新修饰的Tullis旋转剪切设备进行几种动态岩体摩擦实验套件，研究了两种可能调节地震期间断层摩擦行为的机制：热孔隙液压压力弱化（TPW）（TPW）和膨胀硬化（DH）。 TPW的发生是由于摩擦加热的孔隙流体的热膨胀速度比断层孔快。在地震滑动期间排水不佳的条件下，这会导致孔隙压力的增加，从而降低了作用在断层上的剪切应力，从而削弱了断层。 DH具有相反的效果，剪切会导致新的微裂纹的形成增加总孔隙体积，从而降低孔隙流体压力和增强断层。当DH最小时，TPW只有在地震期间才有意义。为了阐明磨损和故障粗糙度在动态摩擦中的作用并探索TPW和DH之间的平衡，PI以滑倒速率进行实验，最高为1 m/s，限制压力（45-60 MPa），孔隙压力升高（25-40 mpa）的限制性（25-40 mpa）在两种渗透率上的范围均可降低表面的范围，并且表面均匀的距离越过压力较大的距离越过压力越过粗糙的距离，该距离是粗糙的，毫无疑问，毫无疑问，越过越野性的粗糙度构成了粗糙度的粗糙度。机械数据将与微结构分析和微力模型结合使用，以指导结果的分析和解释。这些实验将是第一个具有独立控制和升高的孔隙压力，限制压力和正常应力，以1 m/s的速度进行正常应力。它将确定磨损过程在自然断层粗糙度增强的条件下，允许TPW在具有不同渗透率的样品中发展，并且还将确定DH在高位移处的粗糙表面上抵消TPW的程度，该项目由地球科学，地球运动会计划和竞争性研究（Epristive Insfors of Suptiens Isf）的ISF统计的统计数据共同资助。使用基金会的智力优点和更广泛的影响标准，认为通过评估被认为是宝贵的支持。