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

几何复杂断层系统中的破裂传播和停止：分支、跨步和损坏的边界区域

• 批准号: 0809610
• 负责人: James Rice
• 金额: $ 54万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0809610&HistoricalAwards=false
• 关键词: Rupture; Propagation; Arrest; Geometrically; Complex

The project group focuses on a major problem in earthquake science, namely, to understand the interaction of seismic slip-rupture with geometrical and structural complexities of fault zones. Such interactions include transitions of the failure path among fault strands at bends, branches and stepovers, rupture arrest, and induced inelastic deformations in fault border zones, which are generally damaged (highly cracked and/or granulated) and fluid-saturated. Prior work of the group, on which the current studies build, provided new understanding of how rupture paths are chosen at branch-like geometric complexities, and of how inelastic response of the fault bordering zone affects rupture propagation and shear localizations. The new areas for theory and modeling in current work are as follows: (1) Understanding how interactions of deformations with ground fluids and frictional elastic-plastic responses in the damage zone couple to the dynamics of rupture propagation. That includes explaining the effects of different types of across-fault material dissimilarity (in elastic properties, strength and extent of damage, and near-fault permeability to fluids); such dissimilarities are common for mature, highly slipped faults. (2) Assessing if, and to what extent, current understanding of how rupture paths are chosen at branch intersections, and of whether rupture passes through or arrests at step-overs, is affected by the presence of extensively damaged material, capable of elastic-plastic response, near such fault junctions. (3) Determining how residual stress states imprinted in fault-border material by the previous rupture affects response in the next event, and how that depends on rupture directivity in the past and pending events; (4) Devising procedures to rigorously analyze strain localizations that arise in modeling inelastic response of damaged/granulated fault border zones, by imposing localization-limiting procedures that eliminate grid dependence, thus ultimately evolving a methodology that can predict spontaneous development of localized fault-rupture paths through damaged material. Correlation of theory and modeling with field examples and lab experiments is a hallmark of the group's work, and new thrusts in that direction are as follows: (I) Adopting methodology like in (4) above to understanding when a damaged pull-apart stepover, like in the 1992 Landers earthquake between the Johnson and Homestead Valley Faults, and between the Homestead Valley and the Emerson Fault, is breeched by a through-going rupture, and similarly for the 1920 M8 Haiyuan, China event, which ruptured through a sequence of pull-aparts. (II) Understanding mega-branches of great thrust ruptures onto splay faults through the sediment cover of accretionary subduction zones, like documented or suspected at Alaska, Cascadia, Nankai and Sumatra, as well as when and by what processes branching onto landward- versus seaward-vergent splays can occur, and what that means for tsunami generation. (III) Testing the evolving theoretical understanding of rupture branching and interactions with damaged border zones against results of lab experiments (conducted by colleagues elsewhere) which are devised to address the same issues. The understanding of when and how earthquake ruptures stop, which often involves geometric complexities of the type we address, is central to understanding seismic risk. New ways of using relic fault geometries to constrain directivity and other features of past events is also a potentially valuable outcome.

该项目组侧重于地震科学的一个主要问题，即了解地震滑移与断层区域的几何和结构复杂性的相互作用。这种相互作用包括在弯曲，分支和踩踏的断层链之间的故障路径的过渡，破裂停滞以及诱导的断层边界区域中诱导的无弹性变形，这些区域通常损坏（高度破裂和/或颗粒状）和流体饱和。当前研究构建的小组的先前工作提供了对在分支样几何复杂性下如何选择破裂路径的新了解，以及断层边界区域的无弹性响应如何影响破裂的传播和剪切定位。 当前工作中的理论和建模的新领域如下：（1）了解损伤区夫妇对破裂区域的变形与地面流体和摩擦弹性塑性反应的相互作用如何对破裂繁殖动态的相互作用。其中包括解释不同类型的跨反电物质差异的影响（在弹性特性，损害的强度和程度以及对流体的近乎渗透性中）；这种差异对于成熟，高度滑动的故障很常见。 （2）评估在分支交叉点选择破裂路径的当前以及在何种程度上的理解，以及在逐步交流处的破裂是否通过或停止，受到了广泛损坏的材料的影响，能够在此类故障连接附近存在弹性反应的广泛损坏的材料。 （3）确定以前的破裂印记在断层材料中的残留应力状态如何影响下一个事件的反应，以及这如何取决于过去的破裂方向性和未决事件； （4）通过施加限制性限制程序，从而消除了消除网格依赖性的局部化方法，从而使程序进行严格分析在建模受损/颗粒状断层边框区域的非弹性反应时产生的应变局部化，从而最终会发展出一种可以预测通过破坏材料的局部断层破裂路径自发发展的方法。 Correlation of theory and modeling with field examples and lab experiments is a hallmark of the group's work, and new thrusts in that direction are as follows: (I) Adopting methodology like in (4) above to understanding when a damaged pull-apart stepover, like in the 1992 Landers earthquake between the Johnson and Homestead Valley Faults, and between the Homestead Valley and the Emerson Fault, is breeched by a through-going rupture, and同样，对于1920年M8 Haiyuan，中国事件，该事件通过一系列套装破裂。 （ii）通过增生俯冲带的沉积物封面，了解大型推力的巨大分支，例如在阿拉斯加，卡斯卡迪亚，南卡伊和苏门答腊的记录或怀疑，以及何时以及通过分支到陆地上可能发生的陆地上的分支，以及在何时发生的tsunmi spsunami sunermi of to tosunami of to tsunami sunerami senerami ofers of therward and tssunami spersenami。 （iii）测试对破裂分支的理论理解以及与受损边界区域的相互作用与实验室实验结果（由其他地方的同事进行）的结果，这些结果被设计为解决相同的问题。对地震何时以及如何破裂的理解通常涉及我们所解决的类型的几何复杂性，这对于理解地震风险是至关重要的。使用遗物断层几何形状来限制定向性和过去事件的其他特征的新方法也是一个潜在的宝贵结果。