Blind comparison of non-invasive shear wave velocity profiling with invasive methods at bridge sites in Windsor, Ontario

Abstract

Canadian seismic design guidelines classify subsurface ground conditions based on the average shear-wave velocity (VS) of the upper 30 m (VS30). We seek to optimize a robust earthquake site classification procedure for Ontario bridge sites, assessed primarily from blind comparison of non-invasive and invasive shear-wave velocity (VS) depth profiling techniques. Non-invasive seismic testing is performed at 6 bridge sites in Windsor, Ontario co-located with invasive penetration and/or borehole VS measurements. Non-invasive surface wave dispersion and site amplification functions are jointly inverted to retrieve VS profiles at each site. Bridge sites tested are found to be mostly characterized with sediments up to ~30 m thick overlying seismic bedrock. Excellent agreement of VS30 estimates is obtained between both invasive and non-invasive methods and we notably determine an overall average relative difference in VS between methodologies of 9% for soil layers. Earthquake site classification based on VS is consistent at all sites regardless of methodology.