Laboratory Study of Fault Healing and Frictional Properties: Role of Fluids

断层修复和摩擦特性的实验室研究：流体的作用

• 批准号: 0911569
• 负责人: Chris Marone
• 金额: $ 37.46万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-01 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0911569&HistoricalAwards=false
• 关键词: Laboratory; Study; Fault; Healing; Frictional

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This project will investigate slip on tectonic faults and important processes that occur during earthquakes. We will focus on the frictional strength of faults and the role of underground fluids in modifying fault strength. Damaging earthquakes occur on major tectonic faults in a sequence that is often separated by 50 to 100 years or more. One important question for seismic hazard analysis is that of how fault strength is regained between earthquakes ?so called fault healing. This project will investigate fault healing via a combination of detailed laboratory experiments coupled with computational modeling and microscope-based studies of the fault zone textures. Faults in Earth's crust undergo a range of slip behaviors including earthquakes and non-damaging 'creep' events in which slip occurs without releasing damaging seismic waves. One of the goals of this project is to determine the microscopic and larger-scale factors that cause each type of slip behavior. This information will help us build more realistic models for seismic hazard around the country. Results of the project are expected to have significant impact on understanding faults and earthquakes including triggering of seismic and aseismic fault slip, fault interaction, and seismic hazard assessment. Fault healing plays a central role in earthquake rupture processes at time scales ranging from tectonic to elastodynamic. Frictional healing (as evidenced by increasing static friction during quasi-stationary contact) is considered the most likely mechanism of interseismic and dynamic fault strengthening, and there is good agreement between laboratory-based friction laws and field observations of fault healing in some cases. However, laboratory data are limited in quantity and scope. Existing lab data do not provide a consistent explanation of fault healing as observed via repeating earthquakes, which indicate both increases and decreases in seismic moment as a function of time between successive events. Moreover, the physical processes of fault healing and, more generally, the micro-mechanisms of frictional rate/state effects are poorly understood. This project will support a multidisciplinary investigation of fault healing. The work includes two general tasks. 1) Laboratory study of frictional healing and fault zone transport properties for a range of conditions (shearing rate, gouge material, normal stress, fluid properties, temperature). Experiments will be conducted under true-triaxial stress conditions using the double-direct shear configuration with controlled pore fluid pressure and flow through. We will measure healing via frictional strength, elastic properties of the fault zone, and hydraulic transmissivity during shear. Detailed microstructural studies of the deformed samples will be used to identify processes responsible for healing. 2) Coupled numerical, laboratory, and microstructural studies aimed at identifying the physico-chemical processes that determine fault healing, creep consolidation, and time-dependent fault weakening. Preliminary data are available in each area of proposed study

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。该项目将调查地震期间发生的构造断层和重要过程的滑动。我们将着重于断层的摩擦强度和地下流体在改变断层强度中的作用。破坏性地震发生在主要的构造断层上，通常相隔50至100年或更长时间。地震危险性分析的一个重要问题是，断层强度如何在两次地震之间恢复？所谓的故障修复。该项目将通过详细的实验室实验结合计算机建模和基于显微镜的断层带纹理研究来研究断层愈合。 地壳中的断层经历了一系列的滑动行为，包括地震和非破坏性的“蠕变”事件，其中发生滑动而不释放破坏性的地震波。 该项目的目标之一是确定导致每种类型的滑移行为的微观和大尺度因素。这些信息将帮助我们在全国范围内建立更现实的地震危险模型。该项目的结果预计将对理解断层和地震产生重大影响，包括触发地震和地震断层滑动，断层相互作用和地震危险性评估。断层愈合在地震破裂过程中起着核心作用，时间尺度从构造到弹性动力学。 摩擦愈合（证明了在准静态接触过程中增加静摩擦）被认为是最有可能的机制，地震间和动态故障加强，并有良好的协议之间的摩擦定律和现场观察故障愈合在某些情况下。 然而，实验室数据的数量和范围有限。现有的实验室数据没有提供通过重复地震观察到的断层愈合的一致解释，这表明地震矩随着连续事件之间的时间而增加和减少。此外，故障愈合的物理过程，更一般地说，摩擦率/状态效应的微观机制知之甚少。 该项目将支持故障修复的多学科调查。这项工作包括两个总的任务。1)在一系列条件下（剪切速率、断层泥材料、法向应力、流体性质、温度）对摩擦愈合和断层带输运特性进行实验室研究。实验将在真三轴应力条件下进行，使用双直剪配置与控制孔隙流体压力和流量通过。我们将测量愈合通过摩擦强度，断裂带的弹性特性，和剪切过程中的水力transmittance。 变形样本的详细显微结构研究将用于识别愈合过程。2)耦合数值，实验室和微观结构的研究，旨在确定的物理化学过程，确定故障愈合，蠕变固结，并随时间变化的故障弱化。拟议研究的每个领域都有初步数据