Saint John sits on rock that varies from granite to shale, but the real story is the thickness and stiffness of the overburden in the Kennebecasis Valley and along the harbour. A uniform spectral acceleration for the whole city simply does not capture what happens when a 1-in-2,475-year event hits the Carboniferous bedrock versus the compressible clays near the Reversing Falls. Our team applies geophysical arrays and borehole-constrained site response models to produce seismic microzonation output that feeds directly into your structural engineer's NBCC 2020 Site Class determination. For sites with sharp lateral contrasts, we often pair the MASW survey with deeper refraction lines to avoid missing a velocity inversion that could shift a Site Class from C to E. The difference in base shear can swing your foundation cost by a wide margin, so the zoning map becomes a financial tool as much as a safety document.
Seismic microzonation turns a regional hazard into a site-specific risk profile, letting you design for the ground under your foundations, not the average for the whole city.
