Interaction of earthquake rupture with idealized fault inhomogeneities: Effects on rupture speed, slip, and seismic radiation

地震破裂与理想断层不均匀性的相互作用：对破裂速度、滑移和地震辐射的影响

• 批准号: 1321655
• 负责人: Ares Rosakis
• 金额: $ 40万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-15 至 2016-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1321655&HistoricalAwards=false
• 关键词: Interaction; earthquake; rupture; idealized; fault

This study will advance our fundamental understanding of the dynamics and physics of earthquake-producing faults, focusing on the relation between fault features and seismic radiation, with applications to seismic hazard mitigation. One key question this project aims to answer is if the presence of fault inhomogeneities may cause earthquake ruptures to accelerate and propagate at supershear speeds. It is important to understand the conditions under which supershear earthquakes occur, since supershear ruptures can cause much stronger shaking farther from the fault than subshear ones. Can such destructive earthquakes occur on faults in the US, for example, on the San Andreas fault, some parts of which are locked and loaded for the new big one?According to well-established theories, homogeneous faults require a high level of shear stress to propagate at supershear speeds. Yet numerous field observations reveal that supershear earthquakes occur on mature strike-slip faults that operate at low overall levels of shear prestress. Recently, numerical simulations have shown that heterogeneous faults with patches of higher stress or lower strength can transition to supershear speeds under a much wider range of prestress conditions than what is obtained in models with homogeneous strength. Motivated by these findings, we plan to carry out a combined laboratory and numerical study of how the speed of earthquake ruptures, as well as their accumulated slip and resulting seismic radiation, are affected by several fault inhomogeneity features likely to be present on natural faults. We will also investigate the complimentary question of what the radiated wave fields can tell us about the variations in fault properties. In addition to clarifying the dynamics and physics of earthquakes, the developed well-characterized experiments on faults with inhomogeneity can serve as benchmarks for validation of kinematic inversion models and dynamic rupture codes. The new proposed experimental technique for the enhanced characterization of dynamic rupture processes by coupling digital image correlation and high speed photography can become an invaluable tool for studies of transient phenomena in earthquake science and solid mechanics.

这项研究将提高我们对产生地震断层的动态和物理学的基本理解，重点关注断层特征与地震辐射之间的关系，并应用于减轻地震危险。 该项目旨在回答的一个关键问题是，是否存在断层不均匀性的存在可能导致地震破裂会以超速速度加速和传播。重要的是要了解超壳地震发生的条件，因为超壳破裂可能会导致与次毛的震动更强大。这样的破坏性地震会发生在美国的断层上，例如，在圣安德烈亚斯断层上，其中的某些部分被锁定并为新的大型大型锁定吗？根据公认的理论，均匀的断层需要高水平的剪切应力才能以取代速度传播。然而，许多田间观察结果表明，在剪切预应力较低的成熟滑移断层上发生了超声地震。最近，数值模拟表明，与具有均匀强度的模型中相比，在较大的预应力条件下，具有较高应力或较低强度的斑块的异质断层可以过渡到超速速度。在这些发现的激励下，我们计划对地震破裂速度及其积累的滑移和产生的地震辐射进行合并的实验室和数值研究，受到几种断层不均匀性特征的影响。 我们还将调查辐射波场可以告诉我们故障属性的变化的免费问题。除了阐明地震的动力学和物理学外，开发的对具有不均匀性故障的特征良好的实验还可以用作验证运动学反转模型和动态破裂代码的基准。 通过耦合数字图像相关性和高速摄影的新型实验技术，用于增强动态破裂过程的表征，可以成为地震科学和固体力学中瞬时现象的研究的宝贵工具。