A 24-channel seismograph with a sledgehammer source and a spread of 4.5 Hz geophones gets deployed on a Belleville lot. The setup is straightforward: a linear array captures Rayleigh wave dispersion, then inversion software extracts the shear wave velocity profile. In Belleville, the target is clear: a reliable VS30 value for the National Building Code of Canada site classification. The local geology alternates between shallow Ordovician limestone bedrock, glacial till, and pockets of the Champlain Sea clay plain. Each profile reacts differently to surface waves. A stiff till near Highway 401 gives a VS30 above 760 m/s, while a clay deposit south of Dundas Street drops below 180 m/s. The MASW method cuts through this variability in under an hour per line. The data feeds directly into foundation design, seismic hazard assessment, and liquefaction screening. An SPT drilling program often runs parallel to the MASW survey for a complete stratigraphic picture.
A VS30 of 195 m/s versus 820 m/s changes the site class from D to B, directly multiplying the seismic base shear in the Belleville structural design.
