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严重的自然灾害之一。随着人为地震活动的增加，以前地震风险较低的地区（如美国中部）现在正面临与地震有关的危险。过去十年来，美国中部地震活动率的急剧增加，以及这里和加利福尼亚仪器的改进，提供了丰富的数据集，记录了两种截然不同的地质环境下的小到中等规模的地震；一个是由圣安德烈亚斯大断层上的构造运动主导的，另一个是人类活动在不那么连续、较小的断层上引发的地震。这为进一步了解两种情况下地震的控制因素和后果提供了机会。通过研究和比较两个非常不同的变形区域（北加州和俄克拉何马州）的地震及其相互作用，该项目将促进我们对地震物理基本过程的理解，以及它们对构造环境的依赖，并有助于减少地震相关的危害。提高对地震破裂过程和危险参数（地震活动性和地面运动）之间关系的理解，有助于减少地震对当地社区和重要基础设施造成的危害。该分析还将结合地震和工业三维地震数据，这将有助于制定指导方针，以识别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（在公开大学）的教育做出贡献，并为一名早期职业PI（在公开大学）提供支持。所衍生的最先进的地震目录、集群特征和震源参数数据库将为许多研究提供基础输入，并将对地震危害社区和地震物理学的理解产生广泛的兴趣。这些方法和工作流程将融入地震和勘探地震学以及构造地质学课程的活动中。地震的复杂性是控制震源动力学和随之产生的地面运动的一个重要因素，它与发生地震的断层结构的复杂性有关。该项目将使用高质量地震记录和工业三维地震数据，并开发改进的技术来量化复杂性，增强我们对各种时空尺度上基本震源过程的理解。研究重点是震源固有变率及其与地质构造的关系，以及对地震序列演化和地震动模式的影响。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：北加州由圣安德烈亚斯板块边界断层主导，俄克拉何马州的人类活动在低应变率地区诱发地震。谱复杂性和源-时间-函数复杂性将被量化，并将开发自动分类方法来识别复杂地震。高分辨率工业三维地震数据与地震活动性相结合，使我们能够更好地详细了解基底发震断层的特征。多数据集的综合和整合将有助于了解地质构造与地震破裂之间的相互联系。该奖项反映了美国国家科学基金会的法定使命，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.