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

Hong, Isabel, New Brunswick NJ

Investigators

Abstract

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.