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

地震前兆和地震震级的控制：通过数值模拟探讨巨型逆冲断层的行为

基本信息

批准号：
1723249
负责人：
Julia Morgan
金额：
$ 20.58万
依托单位：
William Marsh Rice University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-08-01 至 2021-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1723249&HistoricalAwards=false
关键词：
Earthquake Precursors Controls Magnitudes Probing

项目摘要

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.

沿着俯冲带发生的大地震会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。由于此类地震被定义为重大地质灾害，特别是对于易受大海啸影响的沿海地区，了解对地震规模的控制以及巨型逆冲断层沿线发生地震的预测因素对于美国和世界各地都具有至关重要的社会意义。该项目将为了解这些主要断层如何以及为何发生地震，以及决定地震规模的因素提供新的见解。我们将使用数值模型来模拟此类设置中存在的条件，以预测故障行为。地震引起了人们极大的兴趣，我们的虚拟地震模型将提供一种刺激的方式来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莱斯大学教师培训课程的合作安排来传播我们的科学知识。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系统的建模研究，以检查对俯冲巨型逆冲断层建模的非均质断层数值模拟对地震和地震滑移的控制。与俯冲巨型逆冲断层一致，我们的研究将集中在不对称断层上，其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状况，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）什么控制地震的规模？地震规模是预先确定的吗？如果是的话，是由什么决定的？（2）是否存在任何一致的前兆现象（例如变形）或性质变化可以告诉我们地震滑动的发生？为了解决这些问题，我们将探究模型数据，包括粒子位移、力、堆积排列等，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，以及不断变化的机械性能，例如摩擦、剪胀、强度和刚度。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。我们还将与上面列出的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阐明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，并在莱斯大学正式建立跨学科合作。我们将在国内和国际会议上发布并展示我们的结果。