From the rolling drumlin fields north of Highway 7 to the lacustrine clay plains near the Lake Ontario shoreline, Clarington's subsurface is anything but uniform. A seismic microzonation study here starts with the controlled energy source of a seismic refraction spread—typically a 24-channel geophone array laid across the site—coupled with a multichannel analysis of surface waves (MASW) to capture shear-wave velocity profiles to depths of 30 metres or more. These field techniques allow us to map the spatial variability in Vs30 across a subdivision, industrial park, or infrastructure corridor, translating raw waveforms into the site classification parameters that the National Building Code of Canada (NBCC 2020) requires for structural design. When the overburden is thick and the bedrock deep, which is common in the southern reaches of the Municipality where glacial Lake Iroquois deposited up to 40 metres of silty clay, we supplement surface wave methods with deep borehole testing to calibrate velocity models against actual stratigraphy and sample recovery.
NBCC 2020 site classification is only as good as the velocity profile behind it—and in Clarington, that profile changes block by block.
Methodology and scope
Local ground factors
In Clarington, we frequently encounter a scenario that generic code-based site classification misses: a thin, stiff desiccated crust overlying soft, normally consolidated clay—a classic Lake Iroquois plain profile. A contractor unfamiliar with the local geology might excavate to 2 metres, see hard clay, assume a Site Class C, and proceed with shallow footings on an overconsolidated crust that masks the amplification potential of the 15 metres of soft material beneath. The result: a structure whose natural period aligns dangerously with the site period, amplifying rather than attenuating seismic energy. This is precisely why microzonation matters: it maps the three-dimensional geometry of soil units, identifies impedance contrasts that reflect body waves, and produces a ground motion model that captures basin-edge effects and lateral variability. Skipping this step on a multi-building development in the Energy Park or along the 401 corridor means designing to a single, potentially unconservative site class that ignores the real spatial heterogeneity of the subsurface.
Relevant standards
The applicable standards include NBCC 2020 Division B, Article 4.1.8 for seismic design provisions and site classification; ASTM D4428/D7400 for
Associated technical services
Site-Specific Response Spectra Development
Combining MASW and deep borehole data with 1D equivalent-linear analysis to produce design acceleration spectra, amplification factors (Fa, Fv), and site period estimates that replace NBCC default values for Site Class D, E, or F conditions. Delivered as a geotechnical seismic design brief ready for structural peer review.
Area-Wide Microzonation Mapping
Systematic grid-based geophysical survey across parcels of 2 to 50 hectares, generating Vs30 contour maps, site class zones, and liquefaction susceptibility overlays. Used by municipal planners and developers to inform land-use decisions, setback requirements, and infrastructure routing in Clarington's growth areas.
Liquefaction and Cyclic Softening Assessment
Targeted evaluation of saturated sand lenses and sensitive clay layers using SPT-based triggering analysis (Youd & Idriss) and cyclic laboratory testing. Critical for sites within 2 km of Lake Ontario or along former stream channels where post-glacial deposition created liquefiable horizons.
Typical parameters
Common questions
What does a seismic microzonation study typically cost for a Clarington development project?
How does NBCC 2020 site classification differ from a full microzonation study?
NBCC 2020 classifies a site from A (hard rock) to E (soft soil) based primarily on Vs30 and standard penetration resistance averaged over the upper 30 metres. A full microzonation goes much further: it maps how that classification varies spatially across a site, identifies impedance contrasts that produce wave reflections, and runs 1D or 2D ground response analyses to compute actual surface acceleration time histories. The code gives you one class for one borehole; microzonation gives you the complete picture for an entire development.
Is liquefaction a real hazard in Clarington given we are not on the West Coast?
While Clarington's seismic hazard is lower than coastal British Columbia, the combination of a moderate crustal earthquake (M5–6) and saturated, loose granular deposits can trigger liquefaction locally. We have identified liquefiable sand lenses within the Lake Iroquois deposits and along buried stream channels in the southern part of the Municipality. The NCEER methodology applied to SPT data from our boreholes quantifies the factor of safety against liquefaction at each depth, and we map the Liquefaction Potential Index across the site so structural engineers can decide whether ground improvement or deep foundations are warranted.
How long does a microzonation study take from field work to final report?
A typical timeline for a site-specific microzonation study in Clarington spans four to six weeks. The field work—seismic refraction, MASW, and any calibration boreholes—is usually completed within three to five days depending on site access and survey grid density. Laboratory dynamic testing of soil samples adds approximately two weeks, and the 1D ground response analysis and report preparation take an additional two to three weeks. Larger area-wide mapping projects with multiple survey lines may extend to eight weeks.