Seismic microzonation mapping of Greater Vancouver based on various site classification metrics

The goal of the multi-year seismic microzonation mapping project for Greater Vancouver, British Columbia, Canada, is to produce seismic hazard maps inclusive of local site effects, in particular seismic hazard specific to one-dimensional site response and three-dimensional Georgia sedimentary basin amplification, as well as liquefaction and landslide hazard potential. 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 Greater Vancouver. This study focuses on the comparison of seismic microzonation maps of Greater Vancouver based on up to three seismic site term parameters and their associated classification schemes: 1) the time-averaged shear-wave velocity (Vs) of the upper 30 m (Vs(30)) and associated Canadian National Building Code (NBC) site class; 2) Vs(30)-based site classification proposed for the updated Eurocode 8; 3) site period (T-0) determined from microtremor site amplification spectra; and 4) a hybrid site classification based on T-0 and the average Vs and thickness of soil. 810 Vs(30) and 2,200 T-0 values are determined to evaluate sub-regional differences in these important seismic site parameters in Greater Vancouver. We find that the seismic microzonation of Greater Vancouver depends on the chosen seismic site parameter (Vs(30), T-0, or a combination of parameters) and that classification schemes with greater class divisions are beneficial to communicating the great variability in seismic site conditions in Greater Vancouver. We recommend that either one hybrid classification map or two classification maps of Vs(30) and T-0 together are required for effective communication of the seismic microzonation of Greater Vancouver.

Automated summary

The goal of the seismic microzonation mapping project in Greater Vancouver is to produce inclusive seismic hazard maps considering local site effects such as one-dimensional site response, three-dimensional Georgia sedimentary basin amplification, liquefaction, and landslide hazard potential. The study evaluates the impact of different seismic site characterization measures on microzonation mapping and communication in the area. The comparison of seismic microzonation maps based on different site parameters shows that the classification schemes with greater class divisions are beneficial for effectively communicating the variability in seismic site conditions. It is recommended to use either one hybrid classification map or two classification maps of Vs(30) and T-0 together for effective communication of the seismic microzonation of Greater Vancouver.