OCE-PRF: Structural controls on fault slip behavior and deformation at the Queen Charlotte oceanic-continental transform

OCE-PRF：夏洛特皇后海陆转换断层滑动行为和变形的构造控制

• 批准号: 2205539
• 负责人: Andrew Gase
• 金额: $ 28.24万
• 依托单位: Western Washington University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-01-01 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2205539&HistoricalAwards=false
• 关键词: OCE; PRF; Structural; controls; fault

Dr. Andrew Gase has been awarded an NSF Ocean Sciences Postdoctoral Research Fellowship to examine seismicity and crustal structure along the Queen Charlotte Fault (QFC) with marine seismic datasets. This work will be conducted at Western Washington University with mentor Dr. Emily Roland and in collaboration with co-mentor Dr. Lindsay Worthington from the University of New Mexico. The QCF is a ~900 km-long oceanic-continental tectonic plate boundary offshore Southeast Alaska and British Columbia that accommodates ~5 cm yr-1 of motion between the Pacific and North American Plates and hosts large earthquakes. Despite the importance of understanding the characteristics of this fault for earthquake hazard mitigation, the structure, properties, and slip behavior of the QCF are poorly determined. Seismic monitoring networks near the north-central QCF are sparse; a new temporary array of seafloor seismometers along the fault provides a key opportunity to explore seismicity and mechanical properties. This project will integrate seismic data from earthquake and human-generated sources to address the questions: 1) How is slip distributed across the QCF system in time and space? and 2) To what extent is the nature of fault slip controlled by the crustal architecture of the Pacific and North American Plates? The proposed research will advance our understanding of fault slip behavior at oceanic-continental transform systems through a collaborative mission with U.S. and Canadian scientists who are focusing on related research objectives offshore British Columbia. In addition to the broader impacts of the research, this project will support research assistantships for undergraduate students in seismology at Western Washington University and will enable the PI to participate as an instructor in a 2-week long summer research and STEM education experience for undergraduate students in New Mexico. The QCF exhibits along-strike variations in obliquity and crustal structure that may influence the nature of its seismicity. Convergence angles decrease northward of Haida Gwaii from 10° to ~0° and the north-central QCF is thought to be entirely localized to a narrow ~1 km-wide fault zone along the continental-oceanic crust boundary. These observations conflict with expectations that slip should be more broadly distributed within the weaker plate. Likewise, along-strike variations in crustal structure and fault damage could affect large earthquakes and slip behavior. This project will evaluate two hypotheses: 1) Active deformation along the north-central QCF is localized along a bimaterial fault bounded by oceanic crust and continental crust, and 2) Slip behavior is controlled by along-strike variations in fault damage and oceanic crustal structure. Oceanic plate structures may contribute geometric complexity or variations in material properties that influence local slip behavior. Advanced event detection and location techniques will identify small magnitude earthquakes and swarms that are not currently observable with regional seismic monitoring networks. Seismic tomography using local seismicity recorded on an array of 28 broadband ocean-bottom seismometers and controlled-source seismic data along the north-central QCF will provide unparalleled seismic velocity constraints on fault-zone and crustal properties with three-dimensional tomography. The expected results will provide important constraints on fault properties, crustal structure, and slip behavior that will inform our understanding of oceanic-continental transforms worldwide while also providing new insights into regional earthquake hazards in Southeast Alaska.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.

安德鲁·加斯（Andrew Gase）博士被授予NSF海洋科学博士后研究奖学金，以检查夏洛特皇后断层（QFC）的地震性和地壳结构，并附有海洋地震数据集。这项工作将在西华盛顿大学与艾米莉·罗兰德（Emily Roland）博士一起在西华盛顿大学（Emily Roland）和新墨西哥大学的同事林赛·沃辛顿（Lindsay Worthington）合作。 QCF是大约900公里长的海洋 - 大陆构造板板边界边界，阿拉斯加东南部和不列颠哥伦比亚省，可容纳太平洋和北美板块之间约5厘米的运动，并举行大地震。尽管重要的是了解这种断层在减轻地震危险方面的特征，但QCF的结构，特性和滑移行为的确定很差。 QCF中北QCF附近的地震监测网络很少。沿断层的新临时海底地震仪为探索地震性和机械性能提供了关键的机会。该项目将整合地震和人类生成的来源的地震数据，以解决以下问题：1）如何在时空上分布在QCF系统中的滑移？ 2）断层滑移的性质在多大程度上由太平洋和北美板块的地壳建筑控制？拟议的研究将通过与美国和加拿大科学家的协作使命，以提高我们对海洋 - 汤型转型系统中断层滑移行为的理解，他们着重于不列颠哥伦比亚省海上相关研究目标。除了研究的更广泛影响外，该项目还将为西华盛顿大学的地震学本科生提供研究助学金，并使PI能够参加为期2周的漫长的夏季研究和STEM教育经验，为新墨西哥州的本科生提供了一项为期2周的漫长的夏季研究和STEM教育经验。 QCF在倾斜和地壳结构上表现出可能影响其地震性质的变化。收敛角将Haida Gwaii的北部从10°降低至〜0°，并且中西部QCF被认为完全位于沿连续tal-oceanic-colust边界的狭窄〜1 km宽断层区。这些观察结果与预期应更广泛地分布在较弱的板块中。同样，地壳结构和断层损害的局势变化可能会影响大地震和滑移行为。该项目将评估两个假设：1）沿北北QCF的主动变形沿着双层断层局部，并由海洋壳和大陆壳界定，而2）滑移行为受到断层损害和海洋壳结构的沿袭的控制。海洋板结构可能会导致影响局部滑动行为的材料特性的几何复杂性或变化。先进的事件检测和位置技术将确定少量的地震和群，这些地震和群体目前无法通过区域地震监测网络观察到。使用局部地震性记录在28个宽带海底地震仪和沿中北部QCF的受控源地震数据上的局部地震性的地震层析成像将对断层区域和地壳特性的无与伦比的地震速度约束提供三维层次造影。预期的结果将为断层属性，地壳结构和滑动行为提供重要的限制，这将使我们对全球海洋 - 国际变换的理解，同时还为阿拉斯加东南部地区的区域地震危害提供新的见解。该奖项反映了NSF的立法使命，并通过使用基础的智力上的评估来评估支持NSF的立法任务，并诚实地对其进行了评估。