Collaborative Research: Investigating the role of dynamic strain fields in earthquake triggering processes by simulating full wavefield with 3D seismic velocity structures

观测由附近和远处的其他地震扰动引起的地震，对于了解地震如何发生以及触发地震的机制非常重要。由地震波通过引起的触发地震表明，地震过程不是完全随机的，也不是独立于不连通断层的。例如，2002年发生在阿拉斯加州的迪纳利7.9级地震引发了美国西部的大量地震。为什么地震与通过的地震波相关，这些微小的地面运动是如何引起地震的？更好地了解这些过程将有助于我们对复杂地震破裂过程的基本了解，并有助于通过准确评估下一次地震可能发生的地点和时间来减轻地震危害。该项目将利用新开发的计算工具，并描述触发地震的模式与远距离地震产生的波之间的关系。该项目将开发一种新的统计方法，以识别南加州和加勒比地区的触发地震。这些触发响应的空间和时间演变将在这些感兴趣的地区跨多个故障系统进行检查。该项目支持加州大学圣地亚哥分校和迈阿密大学的科学家之间的合作。研究生、本科生和博士后研究员都将参与该项目。这项工作将对那些研究地震及其相关危害的人产生广泛的兴趣。大地震经常在数千公里外的多个不相连的断层上动态触发地震事件。通过的地震波和触发的地震活动之间的相关性是强大的，但令人困惑。理解动态触发的一个关键挑战是比较表征孕震深度的现实动态应变场以及相关的地震活动性如何随时间和空间演变。该项目旨在系统地模拟地震序列的动态应变场及其与非均匀三维地震速度介质框架内动态触发地震的关系。该项目的主要目标是研究随时间变化的断层带应力状态和断层带材料特性。该项目将首先通过开发一种新的统计方法来识别南加州和加勒比地区的动态触发病例，该方法使用统计数据的分布而不是仅使用统计数据来发现重大病例。该项目将使用高分辨率三维速度模型和SPECFEM三维算法模拟这些情况下的真实动态应变场。该项目计划为加勒比区域开发高分辨率体波速度模型和地震目录。这项工作的一个核心要素是使用区域地震活动的时空迁移模式作为不断变化的应力状态和材料特性的示踪剂，并交叉检查这些模式与全动态wavefields.This奖项的特点反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Observations of earthquakes caused by perturbations from other earthquakes, both close by and far away, are important for understanding how earthquakes happen and the mechanisms that trigger them. Triggered earthquakes caused by passing seismic waves suggest that earthquake processes are not completely random and independent on disconnected faults. For example, the 2002 Denali magnitude 7.9 earthquake in Alaska triggered abundant earthquakes in the western US. Why do earthquakes correlate with the passing seismic waves, and how do these tiny ground motions cause earthquakes? A better understanding of such processes will help our fundamental understanding of complex earthquake rupture processes and will aid in mitigating seismic hazards by accurately assessing where and when the next earthquake may occur. This project will take advantage of newly developed computational tools and characterizing the relationships between the patterns of the triggered earthquakes and the waves generated by distant earthquakes. The project will develop a new statistical approach to identify triggered earthquakes in southern California and the Caribbean region. The spatial and temporal evolutions of these triggering responses will be examined across multiple fault systems in these regions of interest. The project supports a collaboration between scientists at the University of California, San Diego and the University of Miami. Graduate students, undergraduate students, and postdoctoral fellows will all participate in the project. The work will be of broad interest to those who study earthquakes and their associated hazards. Major earthquakes frequently dynamically trigger seismic events at multiple disconnected faults up to thousands of kilometers away. The correlation between the passing seismic waves and triggered seismicity is robust yet puzzling. A key challenge in understanding dynamic triggering is comparatively characterizing the realistic dynamic strain fields at seismogenic depth and how the associated elevated seismicity evolves through time and space. This project aims to systematically model dynamic strain fields of earthquake sequences and their relation to dynamically triggered earthquakes within a framework of heterogeneous 3D seismic velocity media. The primary goal of the project is to investigate the time-dependent fault zone stress state and fault zone material properties. The project will first identify dynamic triggering cases in southern California and the Caribbean region by developing a new statistical approach that uses distributions of statistics instead of the statistics solely to find significant cases. The project will then simulate realistic dynamic strain fields of these cases with high-resolution 3D velocity models and the SPECFEM 3D algorithms. The project plans to develop a high-resolution body wave velocity model and earthquake catalogs for the Caribbean region. A central element of this work is using the spatiotemporal migration patterns of regional seismicity as tracers of the evolving stress state and material characteristics and cross-examining these patterns with characteristics of the full dynamic wavefields.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.