Subduction zone seismic hazards, oceanic crust evolution and paleoclimate reconstruction

The proposed work will investigate natural phenomena that impact our society. The thrust of the proposal is focused on studying subduction and intraslab earthquakes, and the seismic hazards associated with them. Both subduction and intraslab earthquakes are unique to subduction zones, regions of underthrusting where the oceanic plates dip or subduct underneath the continental plates. Subduction earthquakes, generated on the interplate interface, are the largest earthquakes on Earth (magnitudes >8-9). Intraslab earthquakes are generated within subducting oceanic plate and have magnitudes that can be >7-8. Subduction zone earthquakes pose a huge threat to coastal communities as was tragically illustrated in 2004 by the giant magnitude 9.3 Sumatra earthquake and the subsequent tsunami that killed hundreds of thousands of people. This project will test if seismic reflection imaging, supported by wide-angle refraction work, thermal modeling results and seismicity data, can be used for high-resolution mapping of subduction earthquake rupture areas. The same methodology will be used to determine the relationship between the depth of penetration and volume of water stored in the subducting plates, and the observed frequency and maximum magnitude of intraslab seismicity. The anticipated results (e.g., landward limit of subduction earthquake rupture and maximum magnitude of intraslab earthquakes at the Cascadia margin) should provide constraints needed for improved probabilistic seismic hazards maps. Projects like this are important to Canada and Canadians because the northern Cascadia subduction zone is located offshore western Canada. The proposed research will also focus on using ground penetrating radar to image the internal geometry of sand dunes and to study how they evolve through time. Sand dunes are highly sensitive to climate variability and represent valuable archives of past climatic conditions. Ground penetrating radar images will be analyzed together with remote sensing, geochronological dating, and geomorphic mapping results with the goal to reconstruct the Late Quaternary local paleoclimate responsible for the formation of the investigated sand dunes. Recent climate change is of great public interest.