Earthquake Precursors and Controls on Earthquake Magnitudes: Probing the Behavior of Megathrust Faults through Numerical Simulations

沿俯冲带发生的大地震或强震使断层界面的大部分破裂，释放出大量积累的能量，能够造成灾难性的破坏和破坏。由于这样的地震定义了一种主要的地质灾害，特别是对易受大海啸影响的沿海地区来说，了解地震规模的控制及其沿大型逆冲断层发生的预测因素对美国和全世界都具有重要的社会意义。这个项目将提供新的见解，了解地震是如何以及为什么发生在这些主要断层上，以及是什么决定了地震的规模。我们将使用数值模拟来模拟在这种情况下存在的条件，以预测故障行为。地震引起了大众的极大兴趣，我们的虚拟地震模型将提供一种令人振奋的方式，让公众了解自然过程及其影响。我们将通过网页制作和分发地震模拟和相关现象的动画，并通过与当地学校和赖斯教师培训课程的合作安排来传播我们的科学。我们还将开发可用于本科地质学课程的新教材。在这项研究中，我们将进行系统的建模研究，使用粒子动力学模拟来检查在俯冲巨型逆冲后模拟的非均质断层的数值模拟对地震和地震滑动的控制。与俯冲巨型逆冲相一致，我们的研究将集中在应力和强度沿断层长度变化的非对称断层上。我们将使用这些模拟来开发2D和3D滑动事件的目录，然后在事件发生之前，期间和之后探测断层的条件，以深入了解引发不稳定滑动的条件，以及导致失控滑动停止的条件。我们计划解决的首要问题是：(1)是什么控制了地震的大小？地震的大小是预先决定的吗？如果是，又是由什么决定的？(2)是否有任何一致的前兆现象（如变形）或性质变化可以告诉我们地震滑动的开始？为了解决这些问题，我们将探索模型数据，包括颗粒位移，力，包装安排等，以获得应力和应变的直接约束及其在空间和时间上的变化，以及摩擦，剪胀，强度和刚度等不断变化的机械性能。通过这种方式，我们可以探索对地震破裂和其他滑移行为的具体控制。我们还将把与上述属性变化相关的模拟地震目录与自然系统进行比较。我们的模型将有助于澄清导致不同类型地震的断层特征，以及引发和限制地震的过程，从而提高我们在这一领域的知识。该项目将支持一名研究生和一名本科生，并在莱斯大学正式开展跨学科合作。我们将在国内和国际会议上发表和展示我们的研究结果。

Large or great earthquakes that occur along subduction zones rupture large portions of the fault interfaces, releasing substantial accumulated energy capable of causing catastrophic damage and disruption. As such earthquakes define a major geohazard, particularly to coastal areas vulnerable to large tsunami, understanding the controls on earthquake size and the predictors of their occurrence along megathrust faults is of critical societal relevance to the US and around the world. This project will provide new insights into how and why earthquakes occur on these major faults, and what determines how large they can become. We will use numerical modeling to simulate the conditions present in such settings, to predict fault behavior. Earthquakes are of great popular interest, and our models of virtual earthquakes will provide a stimulating way to inform the public about natural processes and their effects. We will prepare and distribute animations of our earthquake simulations and related phenomena by way of a webpage, and communicate our science through collaborative arrangements with local schools and Rice teacher training courses. We will also develop new course materials that can be used in undergraduate geology courses. In this study, we will carry out a systematic modeling study using particle dynamics simulations to examine the controls on seismic and aseismic slip on numerical analogs of heterogeneous faults modeled after subduction megathrusts. Consistent with subduction megathrusts, our research will focus on asymmetric faults in which stress and strength vary along the length of the fault. We will use these simulations to develop catalogs of slip events in both 2D and 3D, and then probe conditions along the fault before, during, and after the events to gain insights into the conditions that initiate unstable sliding, and those that cause run-away slip to stop. The overarching questions we plan to address are: (1) What controls the size of an earthquake? Is earthquake size predetermined, and if so, by what? (2) Are there any consistent precursory phenomena (e.g., deformation) or properties changes that can inform us about the onset of seismic slip? To address these questions, we will probe the model data, including particle displacements, forces, packing arrangements, etc., to obtain direct constraints on stress and strains and their variations in space and time, as well as evolving mechanical properties such as friction, dilatancy, strength, and stiffness. In this way, we can explore specific controls on earthquake rupture and other slip behaviors. We will also compare our catalogs of simulated earthquakes, correlated with the properties changes listed above, with natural systems. Our models will help to clarify the characteristics of faults responsible for different types of earthquakes, and the processes that initiate and limit them, advancing our knowledge in this area. This project will support one graduate student and one undergraduate student, and formalize interdisciplinary collaborations at Rice. We will publish and present our results at national and international meetings.