Origin and Vertical Extent of Damage Zones Around Continental Strike-slip Faults

大陆走滑断层周围破坏带的起源和垂直范围

• 批准号: 1347087
• 负责人: Scott Johnson
• 金额: $ 28.3万
• 依托单位: University of Maine
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-04-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1347087&HistoricalAwards=false
• 关键词: Origin; Vertical; Extent; Damage; Zones

The objectives of this project are to: (1) scale-up a preliminary micromechanical model for grain-scale coseismic damage spanning the seismogenic zone that integrates analytical (electron backscatter diffraction and cathodoluminescence) and computational (asymptotic expansion homogenization) approaches and fully account for the grain-scale elastic interactions among the different minerals in the sample; (2) apply this integrated framework to quantify the effects of damage and other fault-zone microstructure on seismic anisotropy; (3) determine the spatial and temporal pattern of damage and related seismogenic structure around an ancient strike-slip fault (the Norumbega fault in Maine) exhumed from a depth of approximately 10-15 km; (4) develop a conceptual model linking this pattern to the damage structure of active faults observed at the surface; and (5) disseminate open-source software for damage analysis and calculation of bulk elastic stiffnesses and seismic properties of damaged rocks. This software will take input either from electron backscatter diffraction data files of natural microstructures, or synthetic (computer generated) microstructures that can be used in sensitivity analyses among other applications.Strike-slip faults like the San Andreas Fault in California represent major threats to life and property owing to the repeated generation of large earthquakes. During each earthquake, the rocks surrounding the ruptured segment of the fault are fragmented by cracking of individual mineral grains. Over many earthquake cycles, these rocks become so damaged that they strongly affect the elastic properties of the rocks, and therefore the speed and preferred propagation direction of seismic waves. Although these so-called damage zones are of great importance for seismic hazards, a robust mechanical model for how they form is lacking, and there is almost no information on the vertical extent of this damage within active fault zones. Furthermore, there is currently no computational framework available for calculating how progressive damage evolution might affect seismic wave propagation. The combination of modeling and field-based results from this work will allow improved characterization of seismically active areas, including conceptual and wave speed models that can be used to better predict ground shaking directions and intensities. The open-source codes developed in this project will be made available through existing public portals, and will have many community applications including the relationships between microcrack orientation and state of stress, interpretation of seismological data, and analysis of brittle damage and fragmentation of ceramics and advanced composite materials. Recognition of the importance of microfracturing for macroscopic behavior and the ability to treat it quantitatively is growing in both Earth sciences and materials engineering. The results of this project will provide a framework for future efforts in both fields, and for collaborations between them. The project will contribute to the development of a diverse, globally competitive STEM workforce through training of graduate and undergraduate students and in participation of women in STEM.

该项目的目的是：（1）扩展跨谷物刻菌损伤的初步微电模型，涵盖了地震生成区，该模型涵盖了地震生成区，该模型整合了分析（电子反向散射衍射和降压衍射和降压发光）和计算（非脑膨胀均质化）的方法，并充分说明了晶粒尺度上的具有谷物限制的晶尺度互动式的小小的矿物矿物质的分析，以实现样本; （2）应用此集成框架来量化损伤和其他断层区微结构对地震各向异性的影响； （3）从大约10-15 km的深度中挖出的古老的走滑断层（缅因州的Norumbega断层）周围的损害和相关地震结构的空间和时间模式； （4）开发一个概念模型，将这种模式与在表面观察到的活动故障的损伤结构联系起来； （5）传播开源软件，用于损坏分析和计算块状岩石的弹性刚度和地震特性。该软件将从自然微观结构的电子反向衍射数据文件中获取输入，或者可以在敏感性分析中使用的合成（计算机产生的）微观结构，以及其他应用。加利福尼亚州的San Andreas断层（如大地震反复产生了生命和财产）之类的扫射断层。在每次地震期间，断层破裂段周围的岩石通过单个矿物颗粒的破裂而碎裂。在许多地震周期中，这些岩石变得如此受损，以至于它们强烈影响岩石的弹性特性，因此，地震波的速度和首选传播方向。尽管这些所谓的损害区域对于地震危害至关重要，这是它们缺乏形成方式的强大机械模型，并且几乎没有有关该损伤区域内这种损坏区域的垂直范围的信息。此外，目前尚无计算框架可用于计算渐进损伤演化如何影响地震波传播的方式。这项工作的建模和基于现场的结果的组合将允许改进地震活动区域的表征，包括概念和波速模型，可用于更好地预测地面摇动方向和强度。该项目中开发的开源代码将通过现有的公共门户提供，并将具有许多社区应用，包括微裂纹方向和压力状态之间的关系，地震学数据的解释以及对陶器的脆弱损害和碎片化的分析和先进的复合材料。认识到微裂缝对宏观行为的重要性及其定量治疗的能力在地球科学和材料工程中都在增长。该项目的结果将为未来在这两个领域以及它们之间的合作中提供一个框架。该项目将通过培训研究生和本科生的培训以及妇女参与STEM的培训，从而为多样化的全球竞争性STEM劳动力发展做出贡献。

项目成果

Pervasive cracking of heterogeneous brittle materials using a multi-directional smeared crack band model

• DOI: 10.1016/j.ijmecsci.2017.09.016
• 发表时间: 2017-09
• 期刊: International Journal of Mechanical Sciences
• 影响因子: 7.3
• 作者: A. C. Cook;S. Vel;S. E. Johnson