The seismic response between the dense glacial till underlying the Uptown area and the soft, compressible sediments of the Fraser River floodplain in Queensborough can differ by a factor of three or more. A uniform hazard spectrum derived from a regional model simply cannot capture the three-dimensional basin effects and impedance contrasts that govern shaking intensity at a specific property address. Our laboratory team bridges this gap by running site-specific seismic microzonation campaigns that combine deep shear-wave velocity profiling with one-dimensional and two-dimensional site response analyses, delivering the ground motion parameters that structural engineers need to comply with the National Building Code of Canada. In the complex deltaic environment of New Westminster, where the depth to stiff soil can shift dramatically within a single city block, this level of resolution transforms a foundation design from a generic assumption into a calibrated engineering decision. Projects that require liquefaction triggering assessments benefit directly from the integrated CPT testing we perform to constrain the soil behavior type index across the full stratigraphic column.
A site-specific Vs30 value measured on New Westminster's deltaic soils can shift the design spectral acceleration by over 30 percent compared to the default site class assumption.
