Three-Dimensional Distinct Element Simulations of Dynamic Process of Fault Gouge Evolution

断层泥演化动态过程三维离散元模拟

• 批准号: 0711558
• 负责人: Julia Morgan
• 金额: $ 14.8万
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-07-15 至 2011-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0711558&HistoricalAwards=false
• 关键词: Three; Dimensional; Distinct; Element; Simulations

Brittle fault zones undergo continual wear of fault surfaces during slip, whichleads to a continuous variation in fault surface roughness and a progressive increase inthe thickness of the fault gouge zone with net slip. The dynamic changes in gouge zonefeatures may affect fault frictional strength, stability, and earthquake characteristics.Although previous field, laboratory, and numerical studies have made significantprogress in investigating the geometrical and physical properties of fault gouge zones andtheir effects on fault zone frictional and mechanical behavior, these results still providelimited understanding of the complete process of gouge zone development under a widerange of geological settings, and how these materials might affect the earthquake cycle.Recent modifications to the Distinct Element Method (DEM), including additionof interparticle bonding and breakage, allows us to model the fracture process of cohesiverocks, and makes it possible to directly observe gouge accumulation and modification,mimicking natural fault zone deformation. 2-D DEM simulations of gouge evolutionhave successfully reproduced many observations in the field and laboratory, yieldinginteresting findings that have not been reported in previous gouge zone studies. Theseinclude stages of gouge zone development and their dependence on shear displacement,normal stress, and rock strength. These encouraging results suggest the feasibility,necessity, and importance of improving numerical models and extending the currentstudies into the future.This proposal describes a program to simulate the dynamic processes of gougezone evolution, focused on constraining the relationships between gouge thickness, grainsize distribution, shear zone strength, and surface roughness. We will use much largerassemblages that will allow a wider range of surface and particles sizes and geometries,and conduct these simulations in parallel on the new Rice Cray XD1 supercomputer.Results of these numerical experiments will help in interpreting observations of morecomplex natural faults, leading to an improved understanding of fault zone processes.The work will support training of a postdoctural associate, undergraduates, and provide enhanced 3D codes of fault gouge evolution to the community. Understanding how fault zonesdeform can help improve understanding of how faults slip and thus earthquake hazards.

脆性断裂带在滑动过程中经历断层面的不断磨损，导致断层面粗糙度不断变化，断层泥带厚度随着净滑动而逐渐增加。断层泥带特征的动态变化可能影响断层的摩擦强度、稳定性和地震特征，尽管以往的野外、实验室和数值研究在断层泥带的几何和物理性质及其对断层带摩擦和力学行为的影响方面取得了重大进展，这些结果仍然提供了对广泛地质背景下断层泥带发育的完整过程的初步认识，最近对离散单元法（DEM）的改进，包括增加了颗粒间的结合和断裂，使我们能够模拟粘性岩石的断裂过程，并使直接观察断层泥的积累和修改成为可能，模仿自然断层带的变形。断层泥演化的2-D DEM模拟成功地再现了许多野外和实验室观测结果，产生了以前断层泥区研究中没有报道的有趣发现。这包括断层泥带发展的阶段和它们对剪切位移、正应力和岩石强度的依赖。这些令人鼓舞的结果表明了改进数值模型和扩展当前研究的可行性、必要性和重要性。该建议描述了一个程序来模拟断层泥带演化的动态过程，重点是约束断层泥厚度、粒度分布、剪切带强度和表面粗糙度之间的关系。我们将使用大得多的组合，这将允许更广泛的表面和颗粒尺寸和几何形状，并在新的Rice Cray XD 1超级计算机上并行进行这些模拟。这些数值实验的结果将有助于解释更复杂的自然断层的观测，从而提高对断层带过程的理解。这项工作将支持博士后助理，本科生，并为社区提供断层泥演化的增强三维代码。了解断层带是如何变形的，有助于加深对断层如何滑动以及地震危害的理解。