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

Isabel Hong博士获得了NSF EAR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，以解决我们在理解卡斯卡迪亚俯冲带大地震的空间和时间上仍然存在的关键知识空白。利用硅藻在新的地理位置和大地震之间重建沿海陆地水平的变化，将提供对以前未探索的地区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水平变化地质证据的沿海遗址，重建一段时间以来陆地水平变化的历史。一种使用现代硅藻的新统计模型将应用于硅藻化石，以减少不确定性，提供陆地水平变化的定量估计。这些估计将被整合到横跨美国和加拿大的数据集，以提供跨越整个卡斯卡迪亚俯冲区的改进的地震危险图。该教育计划将为人数不足的本科生和研究生提供参与实地和实验室工作的机会。本次调查收集的样本将用于开发海岸灾害课程。对卡斯卡迪亚俯冲带区域地震灾害的准确评估需要对(同震)和(震间)大地震期间构造板块变形的良好约束估计。根据地层记录中的微化石(例如硅藻)传递函数估计沿海陆地水平的变化，是重建过去大地震期间变形的最准确手段。然而，由于缺乏化石组合的现代类似物，硅藻转移函数在卡斯卡迪亚的应用受到限制，这导致了对陆地水平变化的不可靠估计。为了解决这一局限，洪博士使用了一种新的独特方法，将分布在不同海拔地区的硅藻物种进行分组，以减少化石样本和现代样本之间的差异。这些被分组的物种将被用来开发一种新的贝叶斯硅藻转移函数，以减少不确定性，重建整个地震周期中的陆地水平变化。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善太平洋西北部目前的地震危险图。该项目还得到了构造学、海洋地质学和地球物理学项目的资助。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.