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

断层带是决定地震强度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是不可或缺的，以改善地震灾害评估，石油和/或矿石矿物勘探，和地质储存的碳和/或核废料。断层不是一个单一的表面，而是由一个或多个高变形区组成，称为“断层核”，周围是低变形区，称为“损伤区”。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，并且通常记录包括离散裂缝和/或较小断层的分布变形。总之，断层核和破坏带的性质和分布会影响地震波的传播和能量的释放。它们还决定了断层作为地球表面以下流体运动的管道、屏障或管道/屏障组合系统的能力。这项研究的目的是提高我们的知识，如何在断层带的发展过程中，断层核及其周围的损害区随时间的变化。更具体地说，这项研究是限制：1）需要多长时间来发展损害区，特别是与断层核心的发展;和2）流体流动如何通过损害区与通过断层核心在整个故障的寿命。收集到的数据被用作在开放获取、社区开发的StraboSpot数据系统中以数字方式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，这个项目通过参与改进“石头中的故事”，为威斯康星大学麦迪逊分校地质博物馆的外联使命做出了贡献。“石头中的故事”采用了基于探究的叙事风格，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，以检验断层核和损害区的发展是联系在一起的假设-机械上和水文上-在各个断层带的发展过程中。分析的重点是同构造，自生矿物相内断层核和损伤区，提供了一个岩石记录的时间，性质和条件的变形和流体流动在个别断裂带。研究人员正在收集三个免费的数据集。露头和显微构造研究从微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确定了通过不同断层结构迁移的流体的来源和性质，此外还限制了变形的温度条件。最后，一个新的组合的地质年代学分析，便于比较的时间之间的变形和流体流动的断层核及其周围的损害区。这些数据集的整合为断层带结构演化及其对断层力学和流体流动的影响提供了独特的见解，从而提高了对地震活动性和地壳物质传输的理解。该奖项反映了NSF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。

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.