Three Windows in Stress from the Geology of Faults

断层地质应力中的三个窗口

• 批准号: 0948740
• 负责人: Emily Brodsky
• 金额: $ 32万
• 依托单位: University of California-Santa Cruz
• 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: 2010-01-15 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0948740&HistoricalAwards=false
• 关键词: Three; Windows; Stress; Geology; Faults

Knowledge of the absolute stress on faults is as essential to understanding earthquakes as it has proven elusive to measure. The goal of this project is to estimate absolute stress by measuring the response to a stress perturbation caused by fault surface geometry. Geologic features surrounding faults record this stress perturbation in outcrop and include intense cracking in the host rock (damage zones), striations on fault surfaces, and melted rock. Recently, significant progress in generalizing the interrelationships among total fault displacement, surface roughness and damage. In this project surface geometry and fault features are directly linked through detailed observations of along-strike variations. These variations provide measures of how much the surface irregularities perturbed the stress field around the fault. More specifically, the researchers will: (1) measure tensile fracture patterns surrounding rough and smooth faults or sections of faults and use this measurement to calculate the near-field off-fault stress field; (2) measure the deflection of striations away from bumps on fault surfaces and use this measurement to calculate the background stress relative to the perturbing stress; and (3) measure the along-strike variation in pseudotachylyte in relation to fault geometry and use this measurement to calculate a bound on friction.Understanding the stress on faults is critical for understanding earthquakes at the level necessary to calculate risk from a physics-based model. This project is designed to fill in this knowledge gap by focusing on the evidence recorded in geological faults. This combined modeling and fieldwork strategy promises results that can be transferable to other fields of earthquake physics.

了解断层上的绝对应力对于理解地震至关重要，因为事实证明它难以测量。该项目的目标是通过测量对断层表面几何形状引起的应力扰动的响应来估计绝对应力。断层周围的地质特征记录了露头的这种应力扰动，包括主岩（损坏区域）的强烈裂纹、断层表面的条纹和熔化的岩石。最近，在概括总断层位移、表面粗糙度和损伤之间的相互关系方面取得了重大进展。在该项目中，通过对沿走向变化的详细观察，将地表几何形状和断层特征直接联系起来。这些变化提供了表面不规则性对断层周围应力场的扰动程度的测量。更具体地说，研究人员将：（1）测量粗糙和光滑断层或断层部分周围的拉伸断裂模式，并利用该测量结果计算近场断层外应力场； (2) 测量断层表面上条纹远离凸块的偏转，并使用该测量来计算相对于扰动应力的背景应力； (3) 测量与断层几何形状相关的假速水剂的沿走向变化，并使用该测量值来计算摩擦力的界限。了解断层上的应力对于了解地震的关键性在于，其水平必须达到基于物理的计算风险所需的水平。模型。该项目旨在通过关注地质断层记录的证据来填补这一知识空白。这种结合建模和现场工作的策略有望将结果转移到地震物理的其他领域。