EAR-PF: Reconstructing land-level change throughout prehistoric megathrust earthquake cycles at the Cascadia subduction zone

伊莎贝尔洪博士已被授予NSF博士后奖学金，在西蒙弗雷泽大学和中央华盛顿大学开展研究和教育计划，以解决我们在卡斯卡迪亚俯冲带发生大地震的时空理解中仍然存在的关键知识差距。在新的地理位置和大地震之间使用硅藻重建沿海陆地水平变化将提供以前未探索的区域和时间尺度的关键估计。洪博士将通过识别和绘制保存完好的陆地变化地质证据的沿海地点，重建陆地变化的历史。一种新的统计模型，使用当今的硅藻将被应用到化石硅藻提供定量估计的土地水平变化，减少不确定性。这些估计将被整合到跨越美国和加拿大的数据集，以提供跨越整个卡斯卡迪亚俯冲带的改进的地震危险图。教育计划将为代表性不足的本科生和研究生提供机会，让他们参加实地和实验室工作。从这次调查中收集的样本将用于开发沿海灾害课程。准确评估卡斯卡迪亚俯冲带沿着的区域地震灾害，需要对大地震期间（同震）和之间（震间）的构造板块变形进行严格的估计。从微体化石（例如，在地层记录中的（硅藻）转换函数是重建过去大逆冲断层地震期间变形的最精确手段。然而，硅藻转移函数的应用一直受到限制，在卡斯卡迪亚缺乏现代类似物的化石组合，这导致不可靠的估计土地水平的变化。为了解决这一限制，洪博士使用了一种新的独特的方法，将不同海拔高度分布相似的硅藻物种分组，这将减少化石和现代样本之间的差异。分组的物种将用于开发新的贝叶斯硅藻转移函数，以减少不确定性，通过整个地震周期重建土地水平变化。该项目的更广泛影响包括培训古地震学领域的本科生和研究生。这项工作的结果将有助于改进太平洋西北地区目前的地震危险图。 该项目还获得了来自构造学和海洋地质学和地球物理学项目的资助。该奖项反映了NSF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。

Dr. Isabel Hong has been granted an NSF EAR Postdoctoral Fellowship to carry out research and education plans at Simon Fraser University and Central Washington University to address key knowledge gaps that remain in our spatial and temporal understanding of the occurance of great earthquakes in the Cascadia subduction zone. Reconstructions of coastal land-level change using diatoms in new geographic locations and between great earthquakes will provide crucial estimates of previously unexplored regions and timescales. Dr. Hong will reconstruct a history of land-level change through time by identifying and mapping coastal sites with well-preserved geologic evidence of land-level change. A novel statistical model using present-day diatoms will be applied to fossil diatoms to provide quantitative estimates of land-level change with reduced uncertainty. These estimates will be integrated into datasets spanning both the United States and Canada to provide improved seismic hazards maps that span the entirety of the Cascadia subduction zone. The educational plan will provide opportunities for underrepresented undergraduate and graduate students to participate in field- and laboratory-based work. Samples collected from this investigation will be used to develop a coastal hazards curriculum.The accurate assessment of regional seismic hazards along the Cascadia subduction zone requires well-constrained estimates of tectonic plate deformation both during (coseismic) and in-between (interseismic) great earthquakes. Estimates of coastal land-level change derived from microfossil (e.g., diatoms) transfer functions within stratigraphic records are the most precise means to reconstruct deformation during past megathrust earthquakes. However, the application of a diatom transfer function has been limited at Cascadia by the absence of modern analogues for fossil assemblages, which has led to unreliable estimates of land-level change. To address this limitation, Dr. Hong uses a new and unique approach of grouping diatom species with similar distributions across elevation that will reduce the dissimilarity between fossil and modern samples. The grouped species will be used to develop a new Bayesian diatom transfer function to reconstruct land-level change through entire earthquake cycles with reduced uncertainty. Broader impacts of this project include training undergraduate and graduate students in areas of Paleoseismology. The results of this work will help improve current seismic hazard maps in the Pacific Northwest. This project also received funding from the Tectonics and the Marine Geology and Geophysics programs.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.