Collaborative Research: Understanding the Connections Between Strain Transients and Earthquake Swarms

安装了板块边界观测仪，以探测地壳变形加速或减慢的时间段。利用俯冲带逆冲断层、火山正断层和主要走滑断层的大地测量数据，这些以非地震为主的瞬变形变幕现已在世界范围内得到认可。最近的研究证明，这些应变瞬变经常会触发成群的中小地震。到目前为止，对地震和非地震断层滑动的时空分布具有真正高质量约束的少数实例限制了对应变瞬变触发地震的力学理解。本研究将大地测量反演和地震触发研究相结合，改进了将应变瞬变与地震率增加联系起来的力学模型。前人的工作表明，现有的力学模型不能定量地预测地震群在瞬变过程中的随机特性。正在使用GPS网络过滤方法在南加州的索尔顿海槽、俄勒冈州和华盛顿州的卡斯卡迪亚俯冲区以及阿拉斯加俯冲区探测新的应变瞬变。然后使用地震触发的随机和力学模型的组合来分析与任何检测到的瞬变相关联的地震活动，以估计与单个瞬变相关联的速率变化的时间历史。随着这些机械触发模型测试的精度提高，我们对地震触发在不同构造环境中如何工作的理解也在增加。当教师参与科学研究时，他们能够更好地为自己的学生建立科学过程的模型；在科学发现中发挥作用的兴奋直接转化为课堂上的热情。每年从宾夕法尼亚州立大学地球科学教育硕士项目(https://earth.e-education.psu.edu/))招聘的三名教师参加为期10周的研究工作，培训他们分析与大地测量检测到的应变瞬变在时间和空间上相关的地震群目录。这项研究工作和相关指导是他们攻读硕士学位的“顶峰”。他们正在以小组的形式分析与压力瞬变有关的群体，并制定教学计划，将他们的工作结果传播给他们所在学校的中学生。此外，他们正在从这项工作中创建学习对象，这些学习对象将作为宾夕法尼亚州立大学开放教育资源倡议的一部分公开提供。因此，该项目的成果具有前所未有的潜力，既可以创造出地球科学科学家感兴趣的新科学产品，也可以创造出供世界各地中学教师立即使用的新的教学对象。

The Plate Boundary Observatory instruments were installed to detect time periods when the deformation of the Earth's crust speeds up or slows down. These transient, predominately aseismic deformation episodes have now been recognized worldwide using geodetic datasets from subduction zone thrust faults, volcanic normal faults, and major strike slip faults. Recent studies have documented that these strain transients often trigger swarms of small to moderate earthquakes. So far, the small number of examples with truly high-quality constraints on the space-time distribution of both the seismic and aseismic fault slip limits the mechanical understanding of earthquake triggering by strain transients.This study combines geodetic inversions and earthquake triggering studies to improve the mechanical models that connect strain transients with increases in earthquake rate. Previous work shows that current mechanical models do not quantitatively predict the stochastic properties of earthquake swarms during transients. A GPS network filtering approach is being employed to detect new strain transients in the Salton Trough in southern California, the Cascadia subduction zone in Oregon and Washington, and the Alaskan subduction zone. The seismicity associated with any detected transients is then analyzed using a combination of stochastic and mechanical models of earthquake triggering to estimate the temporal history of rate-changes associated with individual transients. As the precision of these tests of mechanical triggering models increases, so does our understanding of how earthquake triggering works in different tectonic environments. When teachers become involved in scientific research, they are better able to model the process of science for their own students; the excitement of playing a role in scientific discovery translates directly to enthusiasm in the classroom. Three teachers per year recruited from Penn State's Master of Education in Earth Sciences program (https://earth.e-education.psu.edu/) participate in a 10-week research effort in which they are trained to analyze catalogs of earthquake swarms that are temporally and spatially correlated to geodetically-detected strain transients. This research effort and related instruction serves as the "capstone" for their master's degree. They are working in teams to analyze swarms related to strain transients as well as to develop teaching plans for disseminating the results of their work to secondary students in their own schools. In addition, they are creating learning objects from this work that will be made publicly available as part of Penn State's Open Educational Resources initiative. Therefore, the results of this project have the unprecedented potential to create both a new science product of interest to EarthScope scientists, and new teaching and learning objects for immediate use by secondary school teachers worldwide.