Development of a Regional Geodatabase and 3D Models of Metro Vancouver and Their Use and Impact to Regional Seismic Hazard Mapping
Abstract
Metro Vancouver faces a significant earthquake hazard due to its proximity to the Cascadia subduction zone. As Metro Vancouver has a high population density, the region's heterogeneous geology which includes uneven, glacially eroded bedrock overlain by thick Quaternary deposits contributes significantly to the heightened seismic risk. Geodata plays an essential role in seismic microzonation mapping. A comprehensive geodatabase specific to western Metro Vancouver is developed from open-source and proprietary sources in combination with field geodata collection to achieve regional seismic microzonation mapping. This geodatabase enabled development of an empirical relationship between standard penetration resistance and shear-wave velocity of Holocene post-glacial sediments, and 3D seismic geology and shear-wave velocity models of Metro Vancouver. The potential impact of a comprehensive regional database of seismic site conditions within Metro Vancouver to seismic hazard assessment is examined in terms of reducing seismic design ground motions of the 2020 National Building Code of Canada based on in situ shear-wave velocity measurements of the top 30 meters. We explore the variability in key seismic site characterization measures most often used for seismic microzonation mapping to evaluate the impact on mapping and communication of seismic microzonation of Metro Vancouver. We find that the seismic microzonation of Metro Vancouver depends on the chosen seismic site parameter and that classification schemes with greater class divisions are beneficial to communicating the great variability in seismic site conditions in Metro Vancouver.