CAREER: Slip rates and earthquake timing of distributed Quaternary crustal deformation to evaluate structural accommodation of clockwise rotation of the Pacific Northwest

历史上，美国太平洋西北地区很少发生破坏性地震，尽管该地区位于地震活跃的卡斯卡迪亚俯冲带之上。这里的地震恢复工作主要集中在离岸卡斯卡迪亚俯冲带及其发生9级地震的可能性上。发生在陆上断层上的破坏性地震，比如西雅图断层，对该地区的威胁也知之甚少。在俄勒冈州，很少有活动断层被发现，但新的激光地形成像（lidar）已经揭示了分布在陆地上的广泛的、以前未知的活动断层。该项目的目的是为这些新发现的断层建立古地震时间和断层滑动率信息，并将其纳入该团队的断层边界地壳块的区域模型，以适应太平洋西北地区的变形。这些信息可以用来更新美国地质勘探局的国家地震危险图和断层样式和活动模型。该项目将通过研究生研究助学金和带薪本科生实习，为女性和代表性不足的少数民族研究生和本科生提供支持，从而扩大代表性不足群体在重要的STEM学科中的参与。它还为早期职业女性首席研究员提供支持。该项目将与俄勒冈州波特兰市的俄勒冈科学与工业博物馆合作，开发一个关于区域构造和地震地质的互动演示展览。这个博物馆合作的主要目标是教育K-12的观众、教师和家长关于地质学、板块构造学、地震科学领域和地震危害的知识。胡安·德·富卡板块的斜向东北俯冲和内华达山脉地块的向北撞击，推动了整个太平洋西北地区相对于稳定的北美的积极顺时针旋转。Geo块体模型将该区域分解为一个有断层边界的旋转块体系统，由类似全球定位系统（GPS）站速度的区域定义。gps定义的块体边界被认为是活动断层的焦点，但并非所有块体边界都与已知的断层系统一致。拟议的项目旨在确定第四纪活动结构，表征其滑动速率，并弥补大地测量确定的块体模型与适应长期地壳旋转平移的地质测绘结构之间的应变预算缺口。该项目旨在通过有针对性的构造地貌和古地震调查，提高对太平洋西北部中部地壳变形的理解，在过去3万年中，断层的速率和时间仍然没有限制。这个时间范围内的数据将弥补大地测量（短期）和基岩（长期）旋转观测之间的差距，并解决块体模型和分布剪切模型之间的差异。本研究收集的数据将评估从GPS速度数据确定的刚性到半刚性块边界的持久性。本文的研究结果将提高我们对全新世至晚更新世太平洋西北旋的复杂地壳调节的认识。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。

Historically, few damaging earthquakes have occurred in the Pacific Northwest region of the United States, although the region overlies the seismically active Cascadia Subduction Zone. Earthquake resilience efforts here have largely focused on the offshore Cascadia Subduction Zone and its potential for magnitude-9 (M9) earthquakes. Damaging earthquakes on onshore faults, such as the Seattle fault, are also a poorly understood threat to the region. Few active faults have been identified onshore in Oregon, but new laser terrain imagery (lidar) has revealed widespread and previously unknown active faults distributed across the landscape. The purpose of this project is to establish paleo-earthquake timing and fault slip rate information for these newly discovered faults and to incorporate them into the team's regional model of fault bounded crustal blocks that accommodate deformation in the Pacific Northwest. This information can be used to update the USGS National Seismic Hazard Map and models of fault style and activity. This project will add to the broadening of participation of under-represented groups in an important STEM discipline, by providing support for female and underrepresented minority graduate and undergraduate students through graduate student research assistantships and paid undergraduate internships in the field of earthquake geology. It also provides for support an early career female principal investigator. The project will collaborate with the Oregon Museum of Science and Industry in Portland, OR, to develop an interactive demo exhibit on regional tectonics and earthquake geology. The primary goal of this museum partnership is to educate K-12 audiences, teachers, and parents about geology, plate tectonics, the field of earthquake science, and earthquake hazards in their community. Oblique northeast-directed subduction of the Juan de Fuca plate and northward impingement of the Sierra Nevada block drive active clockwise rotation of the entire Pacific Northwest region relative to stable North America. Geo block models break the region into a system of fault-bounded rotating blocks, defined by regions of similar global positions system (GPS) station velocities. GPS-defined block boundaries are thought to be the focus of active faulting, but not all block boundaries coincide with a known fault system. The proposed project seeks to identify Quaternary active structures, characterize their slip rates, and to close the strain budget shortfall between geodetically determined block models and geologically mapped structures accommodating translation from long-term crustal rotation. This project is designed to improve understanding of crustal deformation through targeted tectonic-geomorphic and paleoseismic investigations in the central Pacific Northwest where the rates and timing of faulting during the past 30,000 years remain unconstrained. Data in this time range would bridge the observational gap between geodetic (short-term) and bedrock (long-term) observations of rotation and would resolve discrepancies between block models and models of distributed shear. Data collected in this study will evaluate the persistence of rigid to semi-rigid block boundaries determined from GPS velocity data. Results of the proposed study will improve our understanding of complex crustal accommodation of Pacific Northwest rotation in Holocene to late-Pleistocene time.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.