Laboratory Study of Phase III SAFOD Core: Physical Properties and Mechanical Behavior of the Active San Andreas Fault Zone

第三期 SAFOD 核心的实验室研究：活动圣安德烈亚斯断层带的物理特性和力学行为

• 批准号: 0950517
• 负责人: Chris Marone
• 金额: $ 27.55万
• 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: 2010
• 资助国家: 美国
• 起止时间: 2010-04-01 至 2013-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0950517&HistoricalAwards=false
• 关键词: Laboratory; Study; Phase; III; SAFOD

We are working to understand the physical properties of large-scale tectonic faults in Earth's crust, with particular focus on the San Andreas Fault in California. As part of the San Andreas Fault Observatory at Depth (SAFOD) drilling recently penetrated the fault at a depth of ~ 2.5 km. We are studying core recovered during this drilling (SAFOD phase III) along with synthetic fault gouge, samples collected at the surface in the vicinity of the SAFOD borehole, and cuttings from drilling in and around the fault. Only a small amount of core was recovered from the active strand of the fault; therefore, we are using the other materials to expand our data set and investigate physical processes within the fault. Our work is focused on: 1) detailed measurements of frictional properties and permeability of the samples, 2) development of process-based models for controls on fault strength and stability, 3) development of innovative methods to study the role of fault zone fabric on frictional stability and physical properties, and 4) integration of laboratory results with models for fluid flow and heat transport, which will allow critically evaluation of hypotheses for apparent fault weakness. Outstanding questions that we are addressing include: 1) What causes spatial variability in fault slip behavior and seismicity? 2) Are elevated fluid pressures within the SAFOD 3-D volume plausible? 3) How are geophysical observations such as low velocity or resistivity linked to in situ conditions of stress and fluid pressure? 4) Does the fault zone act as a barrier for regional and local fluid flow? 4) Does significant fault healing occur in materials comprising the active SAF, and if so, what is the acoustic (seismic) signature, if any? 5) How are fault zone frictional, elastic, and transport properties linked with those of the surrounding protolith (in other words, how does protolith composition influence fault zone properties)?Our work complements studies by other groups working on SAFOD samples as well as a substantial body of work at Penn State focused on other fault zone drilling projects, such as NanTroSEIZE. Results of the proposed experiments will have societal impact through improved understanding of fault mechanics and earthquake physics, applied to the best-studied and best-instrumented plate boundary fault on Earth.

我们正在努力了解地壳中大规模构造断层的物理特性，尤其关注加利福尼亚的圣安德烈亚斯断层。作为San Andreas断层天文台的一部分，深度（SAFOD）钻孔最近以〜2.5 km的深度穿透了断层。我们正在研究在此钻孔期间回收的核心（SAFOD III期）以及合成断层孔，在Safod钻孔附近的表面收集的样品以及在断层内外钻孔的插条。从断层的活动链中恢复了少量核心。因此，我们正在使用其他材料来扩展数据集并调查故障内的物理过程。我们的工作重点是：1）详细测量摩擦特性和样本的渗透性，2）开发基于过程的模型来控制故障强度和稳定性，3）开发创新方法来研究断层区结构对摩擦稳定性和物理特性的作用，以及4）与流动性流动的模型相结合，将允许流动和热量的繁殖率进行炒作。我们要解决的杰出问题包括：1）是什么导致断层滑移行为和地震性的空间变异性？ 2）SAFOD 3-D体积内的液体压力是否合理？ 3）如何与压力和流体压力的原位条件相关的地球物理观察结果？ 4）断层区是否充当区域和局部流体流动的障碍？ 4）在包含活性SAF的材料中是否发生了明显的断层愈合，如果是的，则声音（地震）特征是什么？ 5）断层区摩擦，弹性和运输特性如何与周围原始石材的摩擦特性相关联（换句话说，原石组成如何影响断层区的性质）？我们的工作补充了其他从事SAFOD样品的小组的研究，以及在宾夕法尼亚州的大量工作，专注于其他断层区钻机项目，例如Nantrose。提出的实验的结果将通过改善对断层力学和地震物理学的理解，并应用于地球上最良性且最具攻击的板边界断层，从而产生社会影响。