Preliminary seismic risk mapping of Nanaimo, British Columbia, for a modeled 9.3 Mw Cascadia megathrust earthquake
Subject
Abstract
Vancouver Island, located at the seismically active convergence of the Pacific, Juan de Fuca, and North American tectonic plates, faces significant earthquake risk. As urban expansion accelerates in the city of Nanaimo, projected to grow by over 40,000 residents by 2046, there is an urgent need to assess the vulnerability of existing and future developments to seismic hazards. This research assessed the spatial distribution of seismic risk across Nanaimo using Geographic Information Systems (GIS) combined with scenario-based modeling in OpenQuake. A 9.34Mw Cascadia megathrust earthquake scenario was employed to estimate structural damage, economic losses, and human nighttime casualty rates. Results indicated that while majority of structures were expected to sustain slight to moderate damage, specific census tracts in the south-central portion of the city exhibited extensive vulnerability, including higher rates of structural collapse. Additionally, emergency response facilities were analyzed for accessibility and vulnerability post-disaster. The findings highlighted the potential isolation of critical services due to roadway disruptions and localized structural damage. This study demonstrated the value of integrating open-source seismic risk modeling with spatial analysis to provide insight into earthquake impacts at the community level.