Collaborative Research: Capitalizing on EarthScope Transportable Array Data to Better Characterize Induced Seismic Sequences

美国中部注水点附近有感地震和破坏性地震的增加引起了公众的关注。鉴于此，人们越来越需要更好地了解这些序列是如何发展的，并教育公众有关诱发地震活动的科学知识。问题是，美国中部和东部的台站密度较低，这意味着许多小震很难用标准的分析师审查技术来识别，而缺乏小震的完整目录极大地阻碍了诱发地震活动的研究。此外，虽然临时网络通常是在序列开始产生显著或有感地震之后部署的，但这些网络错过了诱发地震序列的启动。我们的解决方案是使用EarthScope可移动阵列的数据，建立更完整的目录，更好地描述诱发地震序列的完整特征(包括前后)。为了更好地了解诱发地震活动的震源物理，我们建议通过将新开发的频域检测算法和阵列可视化映射技术应用于可传输的阵列数据，系统地识别位于美国中部和东部流体注入地点附近的目前未编目的小震级地震。使用新检测到的事件，我们将构建一个用作子空间探测器的模板波形目录。这些探测将被用来为八个地理上分散的盆地建立更完整的目录。这些增强的星表将被分析以解决以下问题：(1)在其他星表没有显示地震活动的盆地中是否存在可检测到的事件，或者某些盆地是否是无地震的？(2)我们确定的模板事件在波形特征和/或位置上与先前记录的事件在多大程度上相似？(3)观测到的速率增加符合古登堡-里希特关系，b值是否随时间发生可预测的变化？(4)相对较大的面波通过的瞬时应力是否动态地触发额外的诱发事件或以其他方式改变诱发地震活动的分布？这项研究将更全面地开发频域检测算法和子空间探测器，以识别小地震，并将用于创建新的地震目录，其完整性级别低于大多数现有目录(震级低于2.4级)。这种大的空间尺度分析有可能提供有关诱发地震的新信息，并提供不同地区诱发地震活动普遍存在的定量测量。

The increase in the number of felt and damaging earthquakes near injection sites in Middle America has the public's attention. Given this, there is an ever-growing need to better understand how these sequences develop and to educate the public about the science of induced seismicity. The problem is that the low station density in the central and eastern United States means that many small earthquakes are not easily identified using standard analyst review techniques, and the lack of a complete catalog of small earthquakes greatly impedes induced seismicity studies. Additionally, while temporary networks are often deployed after a sequence has started producing significant or felt earthquakes, these networks miss the initiation of the induced earthquake sequence. Our solution is to use data from the EarthScope Transportable Array, to establish more complete catalogs that better describe the full characteristics (both before and after) of induced seismic sequences. To obtain a better understanding of the source physics of induced seismicity, we propose to systematically identify currently uncataloged small magnitude earthquakes located near fluid injection sites in the central and eastern US by applying a newly developed frequency domain detection algorithm and array visualization mapping techniques to transportable array data. Using newly detected events, we will build a template waveform catalog for use as subspace detectors. The detections will be used to build more complete catalogs for eight geographically dispersed basins. These enhanced catalogs will be analyzed to address the following questions: (1) Are there detectable events in basins where other catalogs show no seismicity or are some basins aseismic? (2) To what extent are the template events we identify similar in waveform characteristics and/or location to previously cataloged events? (3) Are observed rate increases consistent with the Gutenberg-Richter relation and is there a predictable change in b-value with time? (4) Do transient stresses from the passage of relatively large surface waves dynamically trigger additional induced events or otherwise change the distribution of induced seismicity? This study will more fully develop frequency domain detection algorithms and subspace detectors tuned to identify small earthquakes, and will be used to create new earthquake catalogs with magnitude of completeness levels lower (magnitude less than 2.4) than most existing catalogs. This large spatial scale analysis has the potential to provide new information about induced earthquakes and provide a quantitative measure of the ubiquity of induced seismicity in different regions.