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界毁灭性地震的构造加载过程。在过去的十年中，进步使科学家能够捕获和模拟地震周期的一阶特征，但是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，这是因为断层不仅可能在非常故障平面本身上滑落，而且周围受损的岩石也可能会变形以适应板板运动。该项目与台湾国家中央大学的研究人员合作进行，涉及对台湾Chelungpu断层的损伤区样本进行表征，并在这些样品上进行了变形实验，以探索压力下损伤区的行为。更好地理解这种现象将阐明当前地震断层模型中仍缺乏的东西，并提高地震危险分析的准确性。该项目还将通过与台湾科学家进行的强大研究合作以及研究生交换科学思想和文化经验的机会，以培养将在国际协作环境中工作的科学家至关重要的科学思想和文化经验的机会。大多数分析和数值断层力学模型将断层视为嵌入弹性宿主岩石之间的摩擦界面，并且没有考虑到断层平面周围损伤区的特殊特征。但是，即使在地壳条件下，损伤区岩石也可能会发生时间依赖性延性变形，这对剪切应力如何在微观时期发生断层产生重大影响。该项目着重于台湾的切伦普断层，那里从2004年国际大陆钻探项目中回收了高质量的核心材料。 Chelungpu断层系统中断层损伤区域的详细描述将重点放在断裂密度上，然后使用损伤区样品进行蠕变实验来测量时间依赖于时间依赖的应变行为。使用实验室衍生的本构方程，将评估构造条件下损伤区的变形行为。延性本构定律将与数值模型中的断层摩擦特性相结合，以量化每个域，损伤区和断层核心对跨层构造负载过程中总故障变形的相对贡献。许多地球物理观察结果表明，长期尺度（大于一年）可能发生永久性的OFF故障变形。例如，如果从大地研究中推断出的俯冲界面的部分偶联确实是由于稳定的off损变形，则该研究可能会影响对跨层构造负载过程中应力积累过程的理解。