The collective behavior of deep fault asperities during non-volcanic tremor and slow slip

该项目探索了最近发现的一种地球物理现象--非火山震动，其物理来源尚不清楚。这个由多个组成部分组成的项目以协同的方式将理论、观察和实验结合在一起，并聚集了一支在几个领域拥有专业知识的团队：观测地震学、计算建模和实验断裂力学。该项目将利用来自两个不同地区和实验室实验的数据，提供新的观测结果。虽然相关的幕式慢滑瞬变现象以前已经通过模型和实验得到了解决，但非火山地震的模拟和计算模拟才刚刚开始。拟议的研究旨在填补这一空白，同时在大数据集分析、多尺度计算建模以及断裂成像的光学和声学组合技术方面做出贡献。拟议中的研究涉及美国和南美高度暴露于地震危险的地区。了解非地震记忆与孕震带力学之间的关系，这是这一建议所涉及的问题，可以为地震危险性评估提供重要的输入。如果NVT活动被证明是一种自然蠕变仪，它将提供一种远程监测与大地震成核有关的小的无地震滑动瞬变的手段。该项目将为野外实验研究NVT提供新的靶点。这个项目由三个部分组成：(1)一个观测部分，建议在南加州和秘鲁-智利俯冲带的地震波形数据集中系统地搜索NVT；(2)一个理论和计算部分，涉及开发一种多尺度模拟方法，研究在地震和慢滑速率和状态模型中的凹凸体的集体行为及其对瞬变和周期性应力的响应；(3)一个实验部分，将研究瞬时和周期性载荷对断层凹凸体响应的影响。

This project explores a recently discovered geophysical phenomenon, non-volcanic tremor, whose physical origins are not yet known. This multi-component project combines theory, observations and experiments in a synergistic way, and gathers a team with expertise in several areas: observational seismology, computational modeling and experimental fracture mechanics. The project will provide new observations, employing data from two distinct regions and from laboratory experiments. Whereas the related phenomenon of episodic slow slip transients has been previously addressed by models and experiments, analog and computational modeling of non-volcanic tremor is only incipient. The proposed research aims at filling that gap while contributing with innovative methodologies in large dataset analysis, multi-scale computational modelling and combined optical and acoustic techniques for imaging fracture. The proposed studies concern regions of the United States and South America that are highly exposed to earthquake hazard. Understanding the relations between non-vocanic remor and mechanics of seismogenic zones, a question addressed by this proposal, can provide important input for earthquake hazard assessment. If NVT activity proves to be a natural creepmeter it will provide a means to remotely monitor the small aseismic slip transients related to the nucleation of large earthquakes. The project will provide new targets for field experiments to study NVT. It will enhance and diversify the expertise of two post-doctoral fellows and will provide training for a graduate student.This project consists of three components: (1) an observational component proposing a systematic search for NVT in seismic waveform datasets from Southern California and from the Peru-Chile subduction zone; (2) a theoretical and computational component involving the development of a multi-scale modelling approach and studies of the collective behavior of asperities during tremor and slow slip in rate- and- state models and their response to transient and periodic stresses; and (3) an experimental component that will address the effect of transient and periodic loads on the response of fault asperities.