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

合作研究：评估地壳变形对当今会聚边缘构造的贡献：卡斯卡迪亚弧前南部

基本信息

批准号：
1757581
负责人：
Kevin Furlong
金额：
$ 17.03万
依托单位：
Pennsylvania State Univ University Park
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 2022-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1757581&HistoricalAwards=false
关键词：
Collaborative Research Evaluating contribution crustal

项目摘要

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.

俯冲带是地球上最大和最具破坏性的地震的发生地。在两次地震之间，地壳会积累应变，这可以从固定在地面上的GPS标记的逐渐移动中观察到（大地测量观测）。此外，地壳变形的时间跨度更长，达数百万年，例如山脉的隆起。大地测量观测和长期变形之间的关系还不很清楚，特别是在俯冲带的地震危险方面。这个问题在卡斯卡迪亚俯冲带的南端尤其具有挑战性，卡斯卡迪亚俯冲带位于北方加州和南俄勒冈州的近海，那里的地壳受到俯冲和从圣安德烈亚斯断层系统向南转移的构造板块运动的影响。然而，卡斯卡迪亚南部的地质特征使该地区非常适合了解和隔离可能驱动上地壳变形和地震的过程。这些特征包括高地形，高隆起率和高侵蚀率的组合;适合测年的岩石和沉积物;以及三种可能产生地壳变形和俯冲带地震的潜在且可测试的过程。这项研究的目的是更好地了解俯冲带是如何工作的，并预测未来地震的规模和时间。除了研究目标，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，主要为美国印第安学生提供服务。胡帕小学的教师将加入研究小组进行夏季实地考察。该项目的大学教师和学生将与教师一起开展实践活动和实地考察，使六年级学生能够使用真实的数据-这项研究的结果-实践科学研究的每一步。该研究项目还将推进其他预期的社会成果，如妇女和代表性不足的少数民族充分参与STEM，并通过研究生和本科生的培训和早期职业研究人员的支持，发展多元化，具有全球竞争力的STEM劳动力。北美卡斯卡迪亚板块边界南端的标志是从卡斯卡迪亚岩石圈俯冲到圣安德烈亚斯转换断层的过渡。这个复杂的变形区域，即门多西诺三重结，在空间和时间上是可迁移的。局部的岩石隆起和侵蚀速率、阶地形成和河道形态对门多西诺三重连接点和可能的布兰科断裂带（胡安·德富卡板块和戈尔达板块之间的自然地理边界）的向北运动作出了反应。对卡斯卡迪亚前弧上板块的长期变形及其构造驱动因素的了解有限，因此很难在观测到的现今变形模式中隔离地震周期信号。特别是，不同地质信号的叠加-俯冲板块性质的迁移差异和与门多西诺三联点有关的地壳增厚的传播波-需要对一系列时间尺度上的变形和地形变化进行评估。该项目是对南卡斯卡迪亚晚新生代隆起、剥露和侵蚀的综合研究。通过使用对过程的不同速率和定时敏感的多个地质年代学代理（即，根据AHe热年代学[岩石折返1 Ma]、目前隆起的埋藏表面上的宇宙成因放射性核素埋藏年代测定[隆起速率限制在~0- 5 Ma]和宇宙成因放射性核素衍生盆地平均侵蚀速率[过去~ 100 ka的平均值]，将有可能建立一个折返和侵蚀随时间的记录，并探测南部前弧的空间变化。将利用对残余景观遗迹的保护来重建长波长变形/隆起模式，并量化新生代晚期的地貌生产。最后，地球动力学模型将用于探索驱动永久性上板块变形的机制，并解决南部卡斯卡迪亚的构造变形如何影响观测到的大地测量数据中记录的信号。这项研究将有助于通过分离和识别俯冲带的贡献来估计地震危险性。（可恢复的）地震周期变形和构造驱动，该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的评估，被认为是值得支持的。影响审查标准。