The glacial stratigraphy beneath Red Deer presents a stark contrast in seismic response between the compact till uplands and the softer alluvial sediments along the Red Deer River valley. A uniform UHS from the national hazard model cannot capture how the up to 30 meters of interbedded clay, silt, and sand lenses will amplify shaking in the downtown core versus the cleared farmland to the east. We perform seismic microzonation that integrates shear-wave velocity profiling with site-specific response analysis, mapping spectral accelerations at surface level. When the surficial geology varies from stiff till to normally consolidated floodplain deposits within the same project boundary, we often combine deep MASW surveys with borehole SPT drilling to calibrate the velocity model, ensuring the final ground motion parameters reflect true local impedance contrasts rather than generic site class assumptions.
A uniform site class D assignment across Red Deer ignores the 2x amplification differential between till uplands and river valley clays at 0.5 s period.
