Collaborative Research: Systematic Analysis of Dynamic Earthquake Triggering Using the USArray Data

合作研究：利用 USArray 数据系统分析动态地震触发

• 批准号: 1053355
• 负责人: Aaron Velasco
• 金额: $ 24.03万
• 依托单位: University of Texas at El Paso
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-06-01 至 2015-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1053355&HistoricalAwards=false
• 关键词: Collaborative; Research; Systematic; Analysis; Dynamic

Technical description of the project: Although advances are constantly being made in our understanding of the physics governing earthquake rupture, many questions remain. One fundamental question is ?Does a stress threshold exist (i.e., amplitude, frequency, stress orientation, or duration of shaking) for triggering earthquakes?? We propose to test two hypotheses related to earthquake triggering: (1) There exists a minimum dynamic stress threshold (i.e., in amplitude, frequency or both) required to trigger remote earthquakes; and (2) The stresses induced by the passage of seismic waves must align favorably with the local stress field and orientation of faults in order to trigger earthquakes. To test these hypotheses, we will use data collected by stations in EarthScope?s USArray Transportable Array (USArray TA) network, supplemented by local seismic network data when available. The uniform spacing of the USArray TA stations across the contiguous USA will allow us to examine characteristics of remote triggering within a variety of tectonic provinces, background seismicity rates, and within regions of both documented cases of triggered earthquakes and areas of no known triggered earthquakes. For each TA station we will create a catalog high-frequency detections (HFD). We will apply three statistical tests (Binomial, Kolmogorov-Smirnov and Wilcoxon Rank-sum) to determine the significance of HFD rate changes at each station following the surface waves (or S-arrival for local events). Working in tandem with Product Specialists at IRIS, we will augment Ground Motion Visualization (GMV) movies of the temporal evolution of the seismic wavefield to include spatial/temporal markers denoting high-frequency triggers and the orientation of theoretical great-circle paths. We will qualitatively examine these visualizations for signatures of systematic remote earthquake triggering. We test our hypotheses by: (1) Determining the peak dynamic stress and dominant frequency of the passing seismic waves coincident with each of the high-frequency triggers; and (2) Comparing the orientation of the passing seismic waves with the local fault structures and stress field.Non-technical explanation of the project's broader significance and importance: A growing body of scientific studies has demonstrated that the passage of transient signals, or seismic waves, from large earthquakes can remotely trigger small earthquakes thousands of kilometers from an epicenter of a large earthquake. We will systematically investigate triggering using data collected from EarthScope?s USArray Transportable Array (USArray TA) network for global and regional earthquakes, which could provide fundamental insight into the physical mechanisms of earthquake rupture. We will provide the tools and expertise to effectively mine the large USArray dataset (1,000 stations of which 400 are concurrently active; 89,000 earthquakes) for currently unrecognized triggered earthquakes. We will catalog these triggered events by station, thus having a spatial/temporal record for further analysis. We will also develop interactive visualization tools for comparing the spatial and temporal distribution of triggering to the seismic wavefield. The methodology we will develop, and the number of mainshocks systematically processed, have the potential to be transformative in terms of understanding earthquake triggering processes. The University of Texas at El Paso is a Hispanic Serving Institute (HSI) and we will actively recruit undergraduate and graduate students, plus a postdoctoral scholar from underrepresented groups to participate in this project.

该项目的技术描述：尽管我们对地震破裂的物理机制的理解不断取得进展，但仍然存在许多问题。一个基本的问题是，触发地震是否存在应力阈值(即振幅、频率、应力方向或震动持续时间)？我们建议检验两个与地震触发有关的假设：(1)存在触发远程地震所需的最小动应力阈值(即，在幅度、频率上或两者兼而有之)；(2)地震波传播引起的应力必须与局部应力场和断层方向有利地对准，才能触发地震。为了验证这些假设，我们将使用地球示波器？S美国阵列可移动阵列(USArrayTA)台网中的台站收集的数据，并在有本地地震台网数据的情况下进行补充。美国阵列TA台站的均匀间距将使我们能够检查不同构造省份、背景地震活动率以及有记录的触发地震案例和未知触发地震区域内的远程触发特征。对于每个TA站点，我们将创建一个高频检测(HFD)目录。我们将应用三种统计检验(二项检验、柯尔莫戈罗夫-斯米尔诺夫检验和威尔科克逊秩和检验)来确定面波(或局部事件的S-到达)后每个站点的HFD比率变化的意义。与IRIS的产品专家合作，我们将增强地震波场时间演变的地面运动可视化(GMV)电影，以包括指示高频触发和理论大圆路径方向的空间/时间标记。我们将定性地检查这些可视化的系统性远程地震触发的特征。我们通过以下方法来验证我们的假设：(1)确定与每个高频触发器重合的传递地震波的峰值动应力和主频；(2)将传递的地震波的方向与当地的断层构造和应力场进行比较。对该项目更广泛的意义和重要性的非技术性解释：越来越多的科学研究表明，来自大地震的瞬时信号或地震波的传播可以在距离大地震震中数千公里的地方远程触发小震。我们将利用从EarthScope？S美国阵列可移动阵列(USArrayTA)网络收集的数据，系统地研究全球和区域地震的触发作用，这将为地震破裂的物理机制提供基本的见解。我们将提供工具和专业知识，有效地挖掘目前未被识别的触发地震的大型美国地震阵列数据集(1,000个台站，其中400个台站同时活动；89,000个地震)。我们将按站点对这些触发事件进行分类，从而拥有用于进一步分析的空间/时间记录。我们还将开发交互式可视化工具，将触发的时空分布与地震波场进行比较。我们将开发的方法和系统处理的主震数量，在理解地震触发过程方面具有变革性的潜力。德克萨斯大学埃尔帕索分校是一所西班牙裔服务学院(HSI)，我们将积极招收本科生和研究生，以及一名来自代表性不足群体的博士后学者参与这一项目。