Collaborative Research: Roles of rupture complexity, geological structure, stress interaction on earthquake sequences

该奖项全部或部分由2021年美国救援计划法案（公法117-2）资助。地震仍然是社会面临的最重大的自然灾害之一。随着人为地震活动的增加，以前地震风险较低的地区（例如，美国中部）正面临着与地震有关的危险。在过去的十年中，美国中部的地震活动率急剧增加，以及这里和加州改进的仪器提供了两个非常不同的地质环境中记录良好的小型到中型地震的丰富数据集;一个是由大圣安德烈亚斯断层上的构造运动主导的，另一个是人类活动在不太连续的较小断层上诱发地震的。这提供了机会，以了解更多有关的控制因素和地震的后果在这两个设置。通过研究和比较两个非常不同的变形地区（北方加州和俄克拉荷马州）的地震及其相互作用，该项目将促进我们对地震物理学基本过程及其对构造环境的依赖性的理解，并有助于减少与地震有关的灾害。更好地了解地震破裂过程与灾害参数（地震活动性和地面运动）之间的关系有助于减少对当地社区和重要基础设施造成的地震灾害。该分析还将结合联合收割机地震和工业三维地震数据，这将有助于制定准则，以确定俄克拉荷马州潜在的危险临界应力断层。该项目包括在一系列层面上的指导和合作，为两名研究生的教育做出贡献（在2014年），并为职业生涯早期的PI提供支持（在2015年）。所导出的地震目录、地震群特征和震源参数的最新数据库将为许多研究提供基本输入，并将引起地震灾害界的广泛兴趣，以及对地震物理学的理解。这些方法和工作流程将用于地震和勘探地震学以及构造地质学课程的活动。地震的复杂性是控制震源动力学和地震地面运动的一个重要因素，它与发震断层构造的复杂性有关。该项目将使用高质量的地震图和工业3D地震数据，并开发改进的技术来量化复杂性，并提高我们对各种时间和空间尺度上的基本震源过程的理解。研究人员集中在固有的震源变异性，它与地质构造的关系，以及它对地震序列演化和地面运动模式的影响。他们在两个不同的构造环境中对震源和地质断层结构进行了频谱和时域分析：北方加州，主要是由圣安德烈亚斯板块边界断层，以及俄克拉荷马州，人类活动在低应变率地区诱发地震。将量化频谱复杂性和震源时间函数复杂性，并将开发自动分类方法以识别复杂地震。高分辨率工业三维地震资料与地震活动性的配置，使我们能够更详细地了解基底发震断层的特征。多个数据集的综合和整合将有助于理解地质结构和地震破裂之间的相互联系。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Earthquakes remain one of the most significant natural hazards facing society. With the increase of human-induced seismicity, regions that previously had lower seismic risk (e.g., central United States) are now facing earthquake-related hazards. The dramatic increase in the seismicity rate during the past decade in central US, and the improved instrumentation here and in California provide a rich dataset of well-recorded small-to-moderate sized earthquakes in two very different geologic settings; one dominated by tectonic motion on the great San Andreas fault, and the other where human activities induced earthquakes on less continuous, smaller, faults. This provides the opportunity to learn more about the controlling factors and consequences of earthquakes in both settings. By studying and comparing the earthquakes and their interactions in two very differently deforming regions (Northern California and Oklahoma), this project will advance our understanding of the fundamental processes of earthquake physics, their dependence on tectonic setting, and help reduce earthquake related hazards. An improvement in understanding of the relationship between earthquake rupture processes and hazard parameters (seismicity and ground motion) could help to reduce seismic hazard posed to local communities and important infrastructure. This analysis will also combine earthquake and industry 3D seismic data, which will help to develop guidelines to identify potentially hazardous critically stressed faults in Oklahoma. The project includes mentoring and collaboration on a range of levels, contributing to the education of two graduate students (at OU) and support for an early-career PI (at OU). The derived state-of-the-art database of earthquake catalog, cluster characteristics and source parameters will provide fundamental input for many studies, and will be of broad interest to earthquake hazard community, and understanding of earthquake physics. The methods and workflow will feed into activities for classes in earthquake and exploration seismology, and structural geology. The complexity of earthquakes is a significant factor governing earthquake source dynamics and the consequent ground motions, and it is related to complexity in the fault structures on which the earthquakes occur. This project will use both high-quality earthquake seismograms and industrial 3D seismic data, and develop improved techniques to quantify complexity and enhance our understanding of the fundamental earthquake source process on a variety of temporal and spatial scales. The researchers focus on the inherent earthquake source variability, its relationship with geologic structure, and its influence on earthquake sequence evolution and ground motion patterns. They perform a combined spectral and time domain analysis of earthquake sources and geological fault structure in two distinct tectonic settings: northern California which is dominated by the San Andreas plate-boundary fault, and Oklahoma where human activities are inducing earthquakes in a low-strain rate region. Spectral complexity and source-time-function complexity will be quantified, and automatic classification methods will be developed to identify complex earthquakes. Collocated high-resolution industrial 3D seismic data and seismicity enables us to better understand characteristics of seismogenic faults in the basement in detail. The synthesis and integration of multiple datasets will help to understand the interlink between geologic structure and earthquake rupture.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.