Collaborative Research: RUI: Evaluating the contribution of crustal deformation to the present-day tectonics of convergent margins: the southern Cascadia forearc

合作研究：RUI：评估地壳变形对当今会聚边缘构造的贡献：卡斯卡迪亚前弧南部

• 批准号: 1758516
• 负责人: Melanie Michalak
• 金额: $ 15.86万
• 依托单位: Humboldt State University Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-15 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1758516&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Evaluating; contribution

Subduction zones are the sites of the Earth's largest and most damaging earthquakes. Between earthquakes, the Earth's crust accumulates strain, which is observed in gradual movement of GPS markers affixed to the ground (geodetic observations). In addition, the Earth's crust deforms over longer timescales of millions of years, such as the uplift of mountain ranges. The relationship between geodetic observations and long-term deformation is not well understood, especially with respect to earthquake hazards in subduction zones. This problem is particularly challenging at the southern end of the Cascadia Subduction zone, offshore of northern California and southern Oregon, where the Earth's crust is influenced both by subduction and by tectonic plate motion transferred from the San Andreas fault system to the south. However, the geologic characteristics of southern Cascadia make this region well-suited for understanding and isolating the processes that could drive upper crustal deformation and earthquakes. These characteristics include a combination of high topography, high uplift rates, and high erosion rates; rocks and deposits suitable for dating; and three potential, and testable, processes that could generate crustal deformation and subduction zone earthquakes. The goal of this research is to better understand how subduction zones work and to anticipate the size and timing of future earthquakes. In addition to the research objectives, this project includes partnering with faculty at Hoopa Valley Elementary School to develop geoscience field and laboratory exercises for sixth grade students. Hoopa Elementary is located in the heart of the region of scientific focus and serves primarily American Indian students. Hoopa Elementary School teachers will join the research team for summer field work. The project's university faculty and students will join the teachers in developing hands-on activities and field trips that will enable sixth grade students to practice each step of scientific research using real data - the results from this research. The research project would also advance other desired societal outcomes such as full participation of women and underrepresented minorities in STEM and development of a diverse, globally competitive STEM workforce through graduate and undergraduate student training and support of an early career researcher.The southern end of the Cascadia plate boundary in North America is marked by transition from Cascadia lithospheric subduction to San Andreas transform faulting. This complex region of deformation, the Mendocino Triple Junction, is migratory in space and time. Localized rock uplift and erosion rates, terrace formation, and river channel morphology have responded to northward movement of the Mendocino Triple Junction and possibly the Blanco Fracture Zone, which is a physiographic boundary between the Juan de Fuca plate and its Gorda segment. Limited understanding of the long-term deformation in the upper-plate of the Cascadia forearc and its tectonic drivers make it difficult to isolate the earthquake-cycle signal within observed patterns of present-day deformation. In particular, overprinting from different geologic signals - migratory differences in the character of the subducting plate and the propagating wave of crustal thickening associated with the Mendocino Triple Junction - requires an evaluation of deformation and topographic change across a range of timescales. This project is an integrated study of the Late Cenozoic uplift, exhumation and erosion of Southern Cascadia. By using multiple geochronologic proxies that are sensitive to different rates and timings of processes (i.e., AHe thermochronology [rock exhumation 1Ma], cosmogenic radionuclide burial dating on buried surfaces that are presently uplifted [uplift rate constrained from ~0-5Ma], and cosmogenic radionuclide-derived basin averaged erosion rates [averaged over last ~100ka]), it will be possible to develop a record of exhumation and erosion through time and detect spatial variations in the southern forearc. The preservation of relict landscape remnants will be exploited to reconstruct long-wavelength deformation/uplift patterns and to quantify relief production in the Late Cenozoic. Finally, geodynamic models will be used to explore the mechanisms driving permanent upper plate deformation, and address how tectonic deformation of southern Cascadia may impact the signal recorded in observed geodetic data. This research will aid estimation of earthquake hazards at subduction zones by isolating and identifying the contribution of (recoverable) earthquake cycle deformation and of tectonically-driven, geologic time scale deformation at a site well suited to record ongoing tectonic deformation and associated strain.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.

俯冲带是地球最大，最具破坏性地震的地点。在地震之间，地壳积累了菌株，这在固定在地面上的GPS标记的逐渐运动中观察到（大地观测）。此外，地壳在数百万年内的较长时间尺度（例如山脉的隆升）中变形。测量观测与长期变形之间的关系尚不清楚，尤其是在俯冲带中的地震危害方面。这个问题在卡斯卡迪亚俯冲带的南端，北加州和俄勒冈州南部的近海尤其具有挑战性，那里的地壳受俯冲和从圣安德烈亚斯断层系统转移到南部的构造板运动的影响。但是，卡斯卡迪亚南部的地质特征使该区域非常适合理解和隔离可能驱动上皮变形和地震的过程。这些特征包括高地形，高升高率和高侵蚀率的结合；适合约会的岩石和沉积物；以及可能产生地壳变形和俯冲带地震的三个潜力，可检验的过程。这项研究的目的是更好地了解俯冲区是如何工作的，并预测未来地震的规模和时机。除了研究目标外，该项目还包括与Hoopa Valley小学的教师合作，为六年级学生开发地球科学领域和实验室练习。 Hoopa Elementary位于科学重点地区的中心，主要为美国印度学生提供服务。 Hoopa小学教师将加入研究团队进行夏季野外工作。该项目的大学教职员工和学生将与教师一起开发动手的活动和实地考察，这将使六年级的学生能够使用实际数据来练习科学研究的每个步骤 - 这项研究的结果。该研究项目还将推动其他期望的社会成果，例如妇女的充分参与以及代表性不足的少数群体参与STEM和通过研究生和本科生培训和早期职业研究员的支持，并支持多样化，全球竞争性的STEM劳动力。北美的卡斯卡迪亚板边界以从卡斯卡迪亚岩石圈俯​​冲到圣安德烈亚斯变换断层的过渡为标志。这个复杂的变形区域，即Mendocino三重连接，在时空迁移。局部岩石升高和侵蚀率，露台形成和河道的形态已经对Mendocino Triple结的北向运动做出了反应，可能是Blanco断裂带，这是Juan de Fuca板块及其Gorda段之间的生理边界。对Cascadia前臂及其构造驱动器的上层板中长期变形的了解有限，这使得在观察到的当今变形模式中很难将地震周期信号分离。特别是，来自不同地质信号的过度打印 - 俯冲板特征的迁移差异以及与Mendocino Triple Junction相关的地壳增厚的传播波 - 需要评估一系列时间尺度的变形和地形变化。该项目是对已故的新生代隆起，卡斯卡迪亚南部的挖掘和侵蚀的综合研究。通过使用对不同速率和过程敏感的多种测量代理（即，AHE热量学[岩石挖掘1MA]，宇宙生成的放射性核素埋葬约会的日期，这些表面在目前被抬高的埋藏的表面[从〜0-5MA上限制了〜0-5MA]，以及宇宙生成的速度。放射性核素衍生的盆地平均侵蚀率（在最后一个〜100KA中平均）），可以通过时间来发展挖掘和侵蚀的记录，并检测南部前牙的空间变化。保留遗物景观残余物将被利用以重建长波长变形/提升模式，并量化晚期新生代的救生产生。最后，将使用地球动力学模型来探索驱动永久上板变形的机制，并解决南部卡斯卡迪亚南部的构造变形如何影响观察到的地球数据中记录的信号。这项研究将通过隔离和确定（可回收的）地震周期变形和构造驱动的地质时间尺度变形的位点的贡献，来帮助估算俯冲区域的地震危害。反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查标准来评估值得支持。