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: 1053343
• 负责人: Kristine Pankow
• 金额: $ 8.66万
• 依托单位: University of Utah
• 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=1053343&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.

项目的技术描述：尽管我们对控制地震破裂的物理学的理解不断取得进展，但仍然存在许多问题。一个基本问题是？是否存在触发地震的应力阈值（即振幅、频率、应力方向或震动持续时间）？我们建议测试与地震触发相关的两个假设：（1）存在触发远程地震所需的最小动应力阈值（即幅度、频率或两者）； (2)地震波通过引起的应力必须与局部应力场和断层方向相匹配才能引发地震。为了检验这些假设，我们将使用 EarthScope 的 USArray 可移动阵列 (USArray TA) 网络中的站点收集的数据，并在可用时辅以当地地震网络数据。美国邻近地区 USArray TA 站的均匀间距将使我们能够检查各种构造省份内的远程触发特征、背景地震活动率以及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，我们都会创建一个高频检测 (HFD) 目录。我们将应用三个统计检验（二项式、Kolmogorov-Smirnov 和 Wilcoxon Rank-sum）来确定每个站点在表面波（或本地事件的 S 到达）之后 HFD 速率变化的显着性。我们将与 IRIS 的产品专家合作，增强地震波场时间演化的地面运动可视化 (GMV) 影片，以包括表示高频触发的空间/时间标记和理论大圆路径的方向。我们将定性检查这些可视化的系统远程地震触发的特征。我们通过以下方式测试我们的假设：（1）确定与每个高频触发一致的通过的地震波的峰值动态应力和主频率； (2) 将通过的地震波的方向与局部断层结构和应力场进行比较。对该项目更广泛意义和重要性的非技术解释：越来越多的科学研究表明，瞬态信号或地震的通过大地震产生的波浪可以远程引发距离大地震震中数千公里的小地震。我们将使用从 EarthScope 的 USArray 可移动阵列 (USArray TA) 网络收集的全球和区域地震数据系统地研究触发，这可以为地震破裂的物理机制提供基本见解。我们将提供工具和专业知识，以有效地挖掘大型 USArray 数据集（1,000 个监测站，其中 400 个同时活动；89,000 次地震），以发现当前未识别的触发地震。我们将按站点对这些触发事件进行编目，从而获得空间/时间记录以供进一步分析。我们还将开发交互式可视化工具，用于比较触发的空间和时间分布与地震波场。我们将开发的方法以及系统处理的主震数量有可能在理解地震触发过程方面带来变革。德克萨斯大学埃尔帕索分校是一所西班牙裔服务学院（HSI），我们将积极招募本科生和研究生，以及来自代表性不足群体的博士后学者来参与该项目。