MAPPING VERTICAL LAND MOTION AND FLOODING HAZARDS ALONG THE CASCADIA SUBDUCTION ZONE

Inter-seismic deformation associated with the locking of the Cascadia megathrust significantly impacts the estimation of extreme coastal water level return periods along the coast. Traditionally, vertical deformation models for the Cascadia region rely on sparse GNSS observations, which fail to account for shallow deformation due to sediment compaction and spatially varying deformation patterns. In this study, we employed an integrated approach using InSAR techniques calibrated by GNSS estimates to observe vertical land motion at a 50 m resolution within 50 km strip along the coast of Oregon and Washington. Our results indicate that the regions in British Columbia and Olympia Peninsula are experiencing significant uplift of up to 3 - 4 mm/yr. While most parts of the Cascadia region are experiencing uplift, we identified a few subsiding locations, such as the area around Puget Sound in Washington state and the Newport city in Oregon, which are sinking at 1 – 3 mm/yr. We aim to incorporate this high-resolution spatial dataset into a compound flood model, accounting for vertical land motion, a non-climatic factor often overlooked in coastal flood modeling. This integration will provide a more accurate assessment of flood risks, enhancing coastal resilience planning.