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From damage zone to core: quantifying mechanical and hydrological coupling during fault-zone structural evolution

从损伤带到核心：量化断层带结构演化过程中的机械和水文耦合

基本信息

批准号：
1951985
负责人：
Laurel Goodwin
金额：
$ 36.94万
依托单位：
University of Wisconsin-Madison
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-06-01 至 2024-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1951985&HistoricalAwards=false
关键词：
damage zone core quantifying mechanical

项目摘要

Fault zones are important structures that dictate the magnitude and distribution of earthquakes and fluid flow in the earth’s crust. Understanding the evolution of these structures is therefore integral to improved earthquake hazards assessment, petroleum and/or ore-mineral exploration, and geologic storage of carbon and/or nuclear waste. A fault is not a single surface, but rather consists of one or more zones of high deformation, called “fault cores”, surrounded by zones of low deformation, called “damage zones”. Most of the offset across a fault, including earthquake-related motion, occurs within the discrete fault core(s), which typically record intense crushing and grinding of rock. In contrast, damage zones are more diffuse, and typically record distributed deformation including discrete fractures and/or smaller faults. Collectively, the character and distribution of fault cores and damage zones may influence seismic wave propagation and energy release during earthquakes. They also dictate a fault’s ability to act as a conduit, barrier, or combined conduit/barrier system for fluid movement below the Earth’s surface. This research is designed to improve our knowledge of how fault cores and their surrounding damage zones change through time during the development of fault zones. More specifically, this research is constraining: 1) how long it takes to develop damage zones, particularly in relation to the development of fault cores; and 2) how fluid flow moves through damage zones versus through fault cores throughout a fault’s lifetime. The collected data are being used as a test case for digitally storing and sharing multi-disciplinary earth science data sets in the open-access, community-developed StraboSpot Data System. The project is contributing to STEM education by supporting the training of graduate and undergraduate students. Finally, this project contributes to the outreach mission of the University of Wisconsin-Madison Geology Museum by participating in the improvement of “Stories in Stone”, which uses an inquiry-based narrative style to teach the public about earthquake science.The researchers are integrating structural, geochemical, and geochronological analyses to test the hypothesis that fault core and damage zone development are linked – both mechanically and hydrologically – throughout the development of individual fault zones. Analyses are focused on syntectonic, authigenic mineral phases localized within fault cores and damage zones, which provide a rock record of the timing, character, and conditions of deformation and fluid flow in individual fault zones. The researchers are collecting three complimentary data sets. Outcrop and microstructural examination constrain the nature and distribution of fault-zone deformation and mineralization from the meso-to-micro scale. Geochemical and isotopic analyses of authigenic mineral phases determine the source and character of fluids that migrated through distinct fault structures, in addition to constraining the temperature conditions of deformation. Finally, a novel combination of geochronological analyses facilitates a comparison of the timing of deformation and fluid flow between fault cores and their surrounding damage zones. Integration of these data sets provides unique insight into fault-zone structural evolution and its effects on fault mechanics and fluid flow, thereby generating an improved understanding of seismicity and mass transport in the crust.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.

断裂带是决定地震的震级和分布以及地壳中流体流动的重要构造。因此，了解这些结构的演变对于改进地震灾害评估、石油和/或矿产勘探、碳和/或核废料的地质储存都是不可或缺的。断层不是一个单一的表面，而是由一个或多个高变形带组成，称为“断层核”，周围是低变形带，称为“破坏带”。断层上的大部分偏移，包括与地震有关的运动，都发生在离散的断层核心内，这通常记录了岩石的强烈破碎和研磨。相比之下，损伤区更分散，通常记录分布变形，包括离散裂缝和/或较小的断层。总的来说，断层核和损伤带的特征和分布会影响地震过程中地震波的传播和能量的释放。它们还决定了断层作为地下流体运动的管道、屏障或管道/屏障组合系统的能力。本研究旨在提高我们对断层核及其周围破坏带在断层发育过程中如何随时间变化的认识。更具体地说，这项研究是限制性的：1)发育损伤带需要多长时间，特别是与断层核的发育有关；2)在断层的整个生命周期中，流体是如何穿过损伤区，而不是穿过断层核心的。收集到的数据被用作在开放获取、社区开发的StraboSpot数据系统中数字化存储和共享多学科地球科学数据集的测试案例。该项目通过支持研究生和本科生的培训，为STEM教育做出贡献。最后，该项目通过参与“石头上的故事”的改进，为威斯康星大学麦迪逊分校地质博物馆的外展使命做出了贡献，该博物馆使用探究式的叙事风格向公众传授地震科学知识。研究人员正在整合结构、地球化学和地质年代学分析，以检验断层核和破坏带的发展在整个单个断层带的发展过程中是相互联系的——无论是机械上还是水文上。分析集中在断层核和损伤带内的同构造、自生矿物相，这些矿物相提供了单个断裂带变形和流体流动的时间、特征和条件的岩石记录。研究人员正在收集三个互补的数据集。露头和显微构造检查从细观尺度上制约了断裂带变形和成矿作用的性质和分布。自生矿物相的地球化学和同位素分析除了限制变形的温度条件外，还确定了通过不同断层构造迁移的流体的来源和特征。最后，地质年代学分析的新组合有助于断层核及其周围破坏带之间的变形和流体流动时间的比较。这些数据集的整合提供了对断裂带结构演化及其对断层力学和流体流动的影响的独特见解，从而提高了对地壳地震活动性和物质运输的理解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。