Rupture Propagation and Arrest in Geometrically Complex Fault Systems: Bends, Stepovers, and Damaged Border Zones

几何复杂断层系统中的破裂传播和停止：弯曲、跨步和损坏的边界区域

• 批准号: 0440145
• 负责人: James Rice
• 金额: $ 50万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0440145&HistoricalAwards=false
• 关键词: Rupture; Propagation; Arrest; Geometrically; Complex

A major problem in earthquake science is to understand rupture through geometrically complex fault systems with bends, branches and stepovers. Such complexities exert major control over the propagation and arrest of rupture. The understanding when and how ruptures stop, which is often associated with such features, is central to understanding seismic risk. This study continues recent developments of the theory and modeling of fault fracture at encounters with kinks, bends and offsets between fault segments. That is done with close reference to explaining rupture patterns as observed in field examples. Those include branches and stepovers in major strike-slip earthquakes (e.g., 2001 Kunlun, Tibet, 2002 Denali, Alaska, and 1992 Landers, California), and splay thrust faulting like that documented for the 1944 Nankai, Japan, and 1964 Alaska subduction zones, with implications for tsunami generation. The studies open new frontiers in rupture dynamics and the physics of earthquakes. Those include a basic understanding of how rupture paths are chosen through complex fault systems, and of the formulation of appropriate computational models (based on dynamic finite element and boundary integral equation methodology) to analyze slip propagation through kinks and branches. In such cases there are significant, coupled, dynamic changes in both the normal and shear stress components supported by the fault, which pose new challenges to representing fracture propagation. Progress in correlating theory with field (and sometimes lab) examples is providing new ways of looking at fault geometry and evidence about prestress states, and translating that into predictions about rupture paths. An important issue under study is whether relic fault geometries with branches and other complexities can be used to infer the direction of rupture in past events, which is important for identifying regions of most severe ground motion. Also, the work addresses how damage zones along faults evolve by successive ruptures, and how inelastic processes within such zones may interact back with stress transmission to the rupture front and with the dynamics of propagation to generate high frequency seismic wave emission. The project during the previous funding cycle was also effective in aiding the participation of women in research. That includes the co-PI, a graduate student research assistant, and three visiting student interns who completed research on fault rupture as capstone projects in completion of their degree programs elsewhere.

地震科学中的一个主要问题是通过具有弯曲、分支和台阶的几何复杂断层系统来理解破裂。这种复杂性对破裂的传播和停止施加主要控制。了解破裂何时以及如何停止，这通常与这些特征有关，是了解地震风险的核心。本研究延续了断层断裂理论和模型的最新发展，在遇到扭结，弯曲和断层段之间的偏移。这与解释在现场实例中观察到的破裂模式密切相关。这些包括主要走滑地震的分支和跨越（例如，2001年西藏昆仑、2002年阿拉斯加德纳里和1992年加州兰德斯），以及类似于1944年日本南海和1964年阿拉斯加俯冲带记录的张开逆冲断层作用，对海啸的产生产生有影响。 这些研究开辟了破裂动力学和地震物理学的新领域。这些包括如何通过复杂的断层系统选择破裂路径的基本理解，以及制定适当的计算模型（基于动态有限元和边界积分方程方法）来分析通过扭结和分支的滑动传播。在这种情况下，有显着的，耦合的，动态变化的正常和剪切应力分量支持的故障，提出了新的挑战，代表裂缝的传播。将理论与现场（有时是实验室）实例相关联的进展提供了新的方法来看待断层几何形状和预应力状态的证据，并将其转化为对破裂路径的预测。研究中的一个重要问题是，是否可以使用具有分支和其他复杂性的残余断层几何形状来推断过去地震的破裂方向，这对于确定最严重的地面运动区域非常重要。此外，工作地址如何损坏区沿着故障演变连续破裂，以及如何在这些区域内的非弹性过程可能会相互作用的应力传输到破裂前和传播的动态，以产生高频地震波发射。上一个供资周期的项目也有效地帮助妇女参与研究。这包括共同PI，一个研究生研究助理，和三个访问学生实习生谁完成了对断层破裂的研究作为顶点项目，在完成他们的学位课程在其他地方。