Fault Slip and Seismicity in Geometrically Complex Fault Systems

几何复杂断层系统中的断层滑动和地震活动

• 批准号: 0636064
• 负责人: James Dieterich
• 金额: $ 33万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-01-15 至 2010-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0636064&HistoricalAwards=false
• 关键词: Fault; Slip; Seismicity; Geometrically; Complex; Fault; Slip; Seismicity; Geometrically; Complex

This project is investigating processes that control slip and earthquake occurrence on geometrically complex faults. Slip of non-planar faults and fault networks involves interactions and processes that do not occur in standard planar fault models. These include coupled interactions among slip, normal stress, and fault strength (as set by the coefficient of friction and normal stress). In addition, to accommodate geometric incompatibilities, yielding and stress relaxation processes must accompany slip of major through-going faults to prevent the development of pathological stress conditions (or in extreme cases fault lock-up). In the brittle seismogenic crust, yielding is accomplished principally through the development of secondary faults. The fractal-like character of fault systems and fault roughness indicates that slight movements of secondary faults at all scales are necessary to accommodate slip of major through-going faults. The yielding is manifest as coseismic off-fault deformation during earthquakes, as aftershocks, and as diffuse background seismicity. The modeling component of this project employs 2D and 3D implementations of the boundary element method to represent stress interactions among major through-going faults. Yielding and stress relaxation off of the major faults are modeled through explicit representations of slip on secondary faults, and as bulk relaxation using an earthquake rate formulation, which is derived from rate- and state-dependent fault constitutive properties. Use of this formulation affords a way to represent seismicity, yielding, and stress relaxation while incorporating time- and stress-dependencies that are consistent with laboratory observations of fault slip and earthquake phenomena, such as aftershocks and foreshocks. The observational component of the study uses a variety of data sets to test the theoretical results and guide model development. These include characteristic decay of the productivity of background seismicity and aftershocks by distance from major faults, partitioning of off-fault seismicity between aftershocks and background earthquakes, and stress heterogeneity and stress rotations as indicated by focal mechanism solutions. This work could have implications for the occurrence of earthquake and thus seismic hazard analysis. The project will also support a promising postdoctoral fellow.

该项目正在研究控制滑移和地震发生在几何复杂断层上的过程。非平面断层和故障网络的滑移涉及标准平面故障模型中未发生的相互作用和过程。这些包括滑动，正常应力和断层强度之间的耦合相互作用（根据摩擦和正常应力系数设定）。此外，为了适应几何不兼容，屈服和压力放松过程必须伴随着重大通行断层的滑​​移，以防止病理压力状况的发展（或在极端情况下，故障锁定）。在脆弱的地震生成地壳中，屈服主要是通过次要断层的发展来完成的。断层系统的分形特征和故障粗糙度表明，在所有尺度上，次要断层的轻微移动是必要的，以适应主要的通行断层的滑​​动。屈服表现为地震期间，余震和弥漫性背景地震性的coseis震动off损坏。该项目的建模组件采用边界元素方法的2D和3D实现，以表示主要遍布断层之间的应力相互作用。主要断层的屈服和应力松弛是通过次要断层上滑动的明确表示来建模的，并且使用地震速率公式的散装松弛作为散装弛豫，这是源自速率和状态依赖性断层本构特性的。使用这种配方提供了一种表示地震性，屈服和压力放松的方法，同时融合了与断层滑移和地震现象的实验室观察（例如余震和前壳）的实验室观察一致的时间和压力依赖性。研究的观察成分使用多种数据集来测试理论结果并指导模型开发。这些包括背景地震性和余震的特征性衰减，与主要断层的距离，余震和背景地震之间的越野折磨地震性分配，以及应力异质性和应力旋转，如焦点机制溶液所示。这项工作可能对地震的发生和地震危害分析有影响。该项目还将支持有前途的博士后研究员。