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Frictional strength evolution and earthquake nucleation

摩擦强度演化和地震成核

基本信息

批准号：
1834696
负责人：
Robert Viesca
金额：
$ 24.54万
依托单位：
Tufts University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-04-01 至 2025-03-31
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1834696&HistoricalAwards=false
关键词：
Frictional strength evolution earthquake nucleation

项目摘要

Earthquakes are generated by the rupture of geologic faults. Understanding these hazardous events requires developing mathematical model descriptions of sliding friction and fault rupture. Earthquake forecasting relies on these models, which are constrained by laboratory data and assume phenomenological laws. However, model predictions are highly sensitive to the chosen laws. The PI recently developed a new analytical approach to examine such sensitivities. He demonstrated that existing models of earthquake nucleation and slip may preclude a minimum nucleation size (or minimum earthquake size). Such a minimum size was thought to be required in prior fault models. Here, the PI and his team extend this work to unify existing phenomenological laws for fault friction and the understanding of dynamic rupture nucleation. The expected solution can realign the theoretical framework of earthquake physics with growing observational evidence that threatens the paradigm of a minimum earthquake size. Consequently, this project has critical implications for earthquake modeling and forecasting. It also provides support for a graduate student and a postdoctoral associate. This project addresses the fundamentals of the nucleation and propagation of an earthquake-generating fault rupture. Theoretical models of fault rupture are often based on so-called rate- and state-dependent friction laws, where fault strength depends on the slip rate of the host rock as well as its sliding history, or state. Our understanding of the seismological implications of earthquake nucleation and sliding friction relies on these phenomenological laws. Traditionally, these laws are thought to imply that a minimum fault size is necessary to nucleate an earthquake. An increasing body of experimental friction data has led to several formulations for frictional strength evolution. However, these different formulations produce disparate model predictions for earthquake nucleation. The PI recently developed a new analytical perspective in which the occurrence of slip instability and earthquake nucleation in previous formulations are end-members of a non-linear solution. This approach moves past the classic linear perturbation analysis and eliminates the need for a minimum nucleation size. Here, the PI and his team extend this work to a generalized form of the rate- and state-dependent friction law that advances and unifies the understanding of the so-called aging and slip laws. In this effort, the team examines previous and new descriptions of sliding friction, their role in models of the earthquake process and their seismological implications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

地震是由地质断层的破裂引起的。理解这些危险事件需要发展滑动摩擦和断层破裂的数学模型描述。地震预报依赖于这些模型，这些模型受到实验室数据的约束，并假设现象学定律。然而，模型预测对所选定律高度敏感。PI最近开发了一种新的分析方法来检查这种敏感性。他证明了现有的地震成核和滑动模型可能排除了最小成核尺寸（或最小地震尺寸）。这样的最小尺寸被认为是在先前的故障模型中所需要的。在这里，PI和他的团队扩展了这项工作，以统一现有的断层摩擦现象学定律和对动态破裂成核的理解。预期的解决方案可以重新调整地震物理学的理论框架，越来越多的观测证据威胁到最小地震规模的范式。因此，该项目对地震建模和预测具有重要意义。它还为一名研究生和一名博士后提供支持。本计画探讨地震断层破裂的成核与传播的基本原理。断层破裂的理论模型通常基于所谓的速率和状态相关摩擦定律，其中断层强度取决于宿主岩石的滑动速率以及其滑动历史或状态。我们对地震成核和滑动摩擦的地震学意义的理解依赖于这些唯象定律。传统上，这些定律被认为意味着最小的断层尺寸是地震成核所必需的。越来越多的实验摩擦数据导致了几个公式的摩擦强度演变。然而，这些不同的公式产生不同的模型预测地震成核。PI最近开发了一种新的分析视角，在这种视角中，以前公式中的滑动不稳定性和地震成核是非线性解的端元。这种方法超越了经典的线性扰动分析，并消除了对最小成核尺寸的需要。在这里，PI和他的团队将这项工作扩展到速率和状态相关摩擦定律的广义形式，该定律推进并统一了对所谓的老化和滑动定律的理解。在这项工作中，该小组审查了以前和新的滑动摩擦的描述，他们在地震过程模型中的作用及其地震学意义。这个奖项反映了NSF的法定使命，并已被认为是值得支持的，通过评估使用基金会的知识价值和更广泛的影响审查标准。