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Bulk rheology of fault damage zone materials and its implication for interseismic fault mechanics

断层损伤带材料的体流变性及其对震间断层力学的意义

基本信息

批准号：
1727661
负责人：
Hiroki Sone
金额：
$ 33.89万
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：
2017
资助国家：
美国
起止时间：
2017-08-01 至 2021-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1727661&HistoricalAwards=false
关键词：
Bulk rheology fault damage zone

项目摘要

This project aims to better understand the tectonic loading process leading to devastating earthquakes in major plate boundaries. Advances in the past decade allows scientists to capture and simulate first-order characteristics of the earthquake cycle, but challenges remain in understanding the randomness and spatial variability of earthquake phenomena. This project specifically focuses on one of the complexities that may arise due to the fact that faults may not only slip at the very fault plane itself, but the surrounding damaged rock can also deform to accommodate plate motion. The project, carried out in collaboration with researchers from National Central University, Taiwan, involves characterization of damage zone samples from the Chelungpu fault, Taiwan, coupled with deformation experiments on those samples to explore the behavior of the damage zone under stress. Better understanding of such phenomena will illuminate what is still lacking in current earthquake fault models and lead to improved accuracy of seismic hazard analyses. The project would also advance desired societal outcomes through a strong research collaboration with Taiwanese scientists plus the opportunity for graduate students to exchange scientific ideas and cultural experiences essential to foster future generation of scientists who will work in an international collaborative environment.The objective of this study is to characterize the ductile deformational properties of fault damage zone rocks and to evaluate the importance of such behavior on fault mechanics. Most analytical and numerical fault mechanics models treat faults as a frictional interface embedded between elastic host rocks and does not take into account the peculiar characteristics of the damage zone surrounding the fault plane. However, damage zone rocks may undergo time-dependent ductile deformation even under crustal conditions, which has significant consequences on how shear stress develops on a fault during the interseismic period. The project focuses on the Chelungpu fault, Taiwan, where the high-quality core material was recovered from the 2004 International Continental Drilling Project. Detailed description of the fault damage zones in the Chelungpu fault system will be made with emphasis on fracture density, followed by creep experiments using damage zone samples to measure time-dependent strain behavior. Using lab-derived constitutive equations, deformation behavior of the damage zone under tectonic conditions will be evaluated. The ductile constitutive law will be combined with fault frictional properties in a numerical model to quantify the relative contribution of each domains, damage zone and fault core, to the total fault deformation during interseismic tectonic loading. Many geophysical observations suggest that permanent off-fault deformation may be occurring over long time scales (greater than a year). If, for instance, the partial-coupling of subduction interfaces inferred from geodetic studies is indeed due to steady off-fault deformation, the study may impact understanding of the stress accumulation process during interseismic tectonic loading.

该项目旨在更好地了解导致主要板块边界破坏性地震的构造加载过程。过去十年的进步使科学家能够捕捉和模拟地震周期的一阶特征，但在理解地震现象的随机性和空间变异性方面仍然存在挑战。该项目特别关注可能出现的复杂性之一，因为断层不仅可能在断层平面本身滑动，而且周围受损的岩石也可能变形以适应板块运动。该项目是与台湾国立中央大学的研究人员合作进行的，涉及台湾车笼埔断层损伤区样本的表征，以及对这些样本的变形实验，以探索应力下损伤区的行为。更好地理解这些现象将阐明目前地震断层模型中仍然缺乏的东西，并导致地震危险性分析的准确性提高。本研究的目的是通过与台湾科学家的强有力的研究合作，以及为研究生提供交流科学思想和文化经验的机会，以培养未来在国际合作环境中工作的科学家，从而促进预期的社会成果。断层力学行为大多数分析和数值断层力学模型处理断层作为弹性寄主岩石之间的摩擦界面嵌入，并没有考虑到周围的断裂面的损伤区的特殊特性。然而，即使在地壳条件下，损伤区岩石也可能发生随时间变化的韧性变形，这对断层上的剪应力在地震间隔期的发展具有重要影响。该项目的重点是台湾车笼埔断层，那里的高质量岩心材料是从2004年国际大陆钻探项目中回收的。详细描述的断层损伤区在车笼埔断层系统的重点是裂缝密度，其次是蠕变实验使用损伤区样品来测量随时间变化的应变行为。使用实验室推导的本构方程，在构造条件下的损伤区的变形行为进行评估。将韧性本构关系与断层摩擦特性相结合，建立数值模型，定量分析地震间构造加载过程中各区域、损伤带和断层核对断层总变形的相对贡献。许多地球物理观测表明，永久性断层外变形可能发生在很长的时间尺度（大于一年）。例如，如果从大地测量研究中推断的俯冲界面的部分耦合确实是由于稳定的断层外变形，则该研究可能会影响对地震间构造加载过程中应力积累过程的理解。