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

沿着俯冲带发生的大地震破坏了断层界面的大部分，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重大的地质灾害，特别是对易受大海啸影响的沿海地区，了解对地震规模的控制及其沿巨型逆冲断层发生的预测因素，对美国和世界各地具有关键的社会意义。这个项目将提供新的见解，了解地震是如何发生在这些主要断层上的，为什么会发生，以及是什么决定了它们可能会变得多大。我们将使用数值建模来模拟这种设置中存在的条件，以预测故障行为。地震是人们非常感兴趣的，我们的虚拟地震模型将提供一种刺激的方式，让公众了解自然过程及其影响。我们将通过网页的方式准备和分发我们的地震模拟和相关现象的动画，并通过与当地学校和莱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课程材料。在这项研究中，我们将利用粒子动力学模拟进行一项系统的模拟研究，以检验在俯冲巨型逆冲作用下模拟的非均质断层对地震和无震滑动的控制作用。与俯冲巨型逆冲一致，我们的研究将集中在不对称断层上，在这些断层中，应力和强度沿断层长度变化。我们将使用这些模拟来开发2D和3D滑动事件目录，然后探测事件发生之前、期间和之后沿断层的条件，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规模？地震的大小是预先确定的吗？如果是的话，是通过什么预先确定的？(2)是否有任何一致的前兆现象(例如，形变)或性质变化可以告知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、堆积安排等，以获得对应力和应变及其在空间和时间上的变化的直接约束，以及不断变化的力学性能，如摩擦、剪胀、强度和刚度。这样，我们就可以探索对地震破裂和其他滑动行为的具体控制。我们还将把我们的模拟地震目录与自然系统进行比较，这些目录与上面列出的属性变化相关。我们的模型将有助于阐明导致不同类型地震的断层的特征，以及引发和限制它们的过程，促进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，并使莱斯大学的跨学科合作正规化。我们将在国家和国际会议上公布和展示我们的成果。

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.