A cone penetration rig pushes into the silty clay till north of the Thames River, its seismic module capturing shear wave arrivals every 50 centimetres. That same rig deploys on a vacant lot near White Oaks, where the underlying Kettleby till tells a story most builders miss: London sits on complex glacial deposits that amplify ground shaking in ways a simple seismic hazard map will never reveal. Site class varies block by block here, from dense till to softer lacustrine clay pockets south of Commissioners Road. Microzonation bridges the gap between the national seismic hazard model and what actually happens beneath a specific foundation. We run multi-method surveys — downhole seismic, MASW, and borehole velocity profiling — to produce site-specific response spectra that inform structural design. For deeper soil columns near the river, combining microzonation with CPT testing provides continuous stratigraphy and a direct check on the shear wave velocity profile.
London’s glacial stratigraphy can shift site class from C to E within 100 metres — NBCC 2020 requires site-specific spectra for anything beyond Class C.
Our approach and scope
Site-specific factors
NBCC 2020 requires a site-specific seismic hazard analysis when Site Class E or F conditions are suspected, and London’s geology triggers that threshold more often than many developers realize. The glaciolacustrine silts and clays that underlie downtown and the floodplain can degrade from Site Class C to E within a single city block. If the geotechnical report defaults to the ‘assumed’ Class C without verification, the structural designer may under-design lateral force-resisting elements by 30 percent or more. We have seen this exact scenario on mid-rise projects along Dundas Street, where the savings from skipping microzonation evaporated the moment the building official requested site-specific spectra. The Ontario Building Code references NBCC 2020, and by extension CSA A23.3 for concrete seismic detailing — both assume the ground motion input is correct. Get that wrong and every subsequent calculation drifts further from reality.
Applicable standards
NBCC 2020 — National Building Code of Canada (seismic provisions), CSA A23.3:19 — Design of Concrete Structures (seismic detailing), ASTM D7400 — Standard Test Methods for Downhole Seismic Testing, ASTM D5777 — Standard Guide for Seismic Refraction, Ontario Building Code O.Reg. 332/12 as amended
Other technical services
Site-Specific Ground Motion Analysis
Multi-method Vs profiling (downhole seismic, MASW, SCPT) tied to NBCC 2020 uniform hazard spectra. We produce design spectral acceleration curves for the full period range required by your structural team.
Liquefaction and Site Class Verification
When London’s buried channel sands or loose fill are present, we couple microzonation with cyclic liquefaction analysis so the foundation design reflects both amplified shaking and potential ground failure in one coherent report.
Typical parameters
Quick answers
When does the City of London building department require a site-specific seismic study?
Whenever Site Class E or F conditions are identified during the geotechnical investigation, or when the project falls under post-disaster importance category per NBCC 2020. In practice, many London sites with soft clay pockets or fill exceeding 3 metres trigger this requirement.
What’s included in a typical microzonation deliverable for a London mid-rise project?
A report containing measured Vs30 values, site class determination, design spectral acceleration curves for short and long periods, soil column fundamental period, and a site response summary that the structural engineer can input directly into their ETABS or SAP2000 model.
How long does a microzonation field program take in London?
Fieldwork for a typical 1–3 acre site runs 2 to 4 days using a combination of MASW lines and downhole seismic in boreholes. The interpretive report follows within 10 business days, though we can expedite for projects facing permit deadlines.
What’s the typical budget range for seismic microzonation in London Ontario?
Depending on site size and number of measurement points, microzonation studies in London typically range from CA$4,940 for a single-location verification to CA$24,760 for a multi-method survey across a full city block with liquefaction integration.