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NORTH BAY ONTARIO
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Home › Seismic › Seismic microzonation

Seismic Microzonation North Bay Ontario

Technical studies that support your project.

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North Bay sits on the western edge of the Ottawa-Bonnechere Graben, a seismically active rift system. The 1935 Timiskaming earthquake (M6.2) produced Modified Mercalli Intensity VI shaking here. Glacial Lake Algonquin deposited thick sequences of varved silty clay across the lowlands, while the Canadian Shield granite outcrops on Airport Hill. NBCC 2020 places North Bay in a moderate seismic hazard zone. Site class varies from hard rock (Class A) to soft clay (Class E) within 500 meters. A seismic refraction survey maps bedrock depth and lateral velocity contrasts. For deep soft soil profiles, the MASW method yields Vs30 and fundamental site period data essential for ground response analysis.

Two sites 400 meters apart in North Bay can differ by two NBCC site classes. Microzonation captures that spatial variability.

Our service areas

Investigation

Exploratory test pit ›CPT (Cone Penetration Test) ›SPT (Standard Penetration Test) ›
VIEW ALL INVESTIGATION ›

In-Situ Testing

Field density test (sand cone method) ›Plate load test (PLT) ›Field permeability test (Lefranc/Lugeon) ›
VIEW ALL IN-SITU TESTING ›

Laboratory

Grain size analysis (sieve + hydrometer) ›Triaxial test ›Atterberg limits ›
VIEW ALL LABORATORY ›

Process and scope

Site response differs markedly between the Precambrian rock of the hilltops and the deep lacustrine clay in the Chippewa Creek corridor. A building on granite near Nipissing University may see peak ground acceleration 40% lower than a structure on 30 meters of silty clay near the waterfront. Our approach uses a combination of downhole seismic testing and surface wave techniques.
  • Vs30 mapping per NBCC 2020 Table 4.1.8.4.A
  • Site period estimation from HVSR and MASW field data
  • 1D equivalent-linear ground response using DEEPSOIL or SHAKE2000
  • Microtremor array measurements for basin edge effects
The transition zones between rock and deep soil create complex 2D amplification patterns. A liquefaction assessment becomes critical where loose saturated sands are interbedded within the clay sequence.
Seismic Microzonation North Bay Ontario
Technical reference — North Bay Ontario

Site-specific factors

The sharp impedance contrast between glacial clay and Shield bedrock generates significant ground motion amplification. North Bay's varved clays exhibit strong anisotropy; horizontal shear wave velocity can be 30% lower than vertical. This affects site period calculations. The Chippewa Creek floodplain contains pockets of loose saturated sand. During a moderate earthquake, pore pressure buildup in these lenses could trigger cyclic softening. Basin edge effects along the escarpment north of Trout Lake produce constructive wave interference. A 1D analysis underestimates surface motion in these zones by up to 25%. We run 2D finite-element models using QUAD4M or equivalent to capture lateral wave propagation. The frost depth of 1.8 meters in North Bay also affects near-surface stiffness seasonally. Winter frozen crust increases Vs30 temporarily; summer thaw reduces it.

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Applicable standards

NBCC 2020 (National Building Code of Canada, Part 4, Division B), CSA A23.3-19 (Design of Concrete Structures, seismic provisions), ASTM D7400-19 (Downhole Seismic Testing), ASTM D5777-18 (Seismic Refraction), Geological Survey of Canada Open File 8320 (Seismic Hazard Model)

Reference parameters

ParameterTypical value
Vs30 range (local soils)180 m/s to > 1500 m/s
Fundamental site period0.05 s (rock) to 0.8 s (deep clay)
NBCC 2020 site classes mappedA, C, D, E
Depth to bedrock (lowlands)5 m to > 40 m
Design PGA (Sa 0.2, Class C)0.33 g (NBCC 2020)
Measurement array spacing50 m to 200 m grid
Testing depth (MASW)30 m typical, 60 m deep profiles
Amplification factor range1.1 to 2.8 (short period)

Quick answers

What seismic hazard zone is North Bay Ontario in?

NBCC 2020 classifies North Bay within a moderate seismic hazard region. The 2% in 50-year design PGA on firm ground (Site Class C) is approximately 0.33 g. Local site conditions can amplify this significantly. Deep clay sites near the waterfront may experience short-period spectral acceleration (Sa 0.2) exceeding 0.55 g.

How is site class determined for a property in North Bay?

Site class follows NBCC 2020 Table 4.1.8.4.A based on Vs30. Field measurement is required. We use MASW or downhole seismic to obtain the average shear wave velocity in the top 30 meters. For shallow bedrock sites on the Shield, Vs30 exceeds 1500 m/s (Class A). Deep clay sites often fall into Class D or E.

What is the cost of a seismic microzonation study in North Bay?

Microzonation studies in North Bay range from CA$5,280 for a single-site Vs30 measurement with site class determination, up to CA$23,250 for a multi-hectare grid with 2D ground response analysis, GIS deliverables, and design spectra generation for structural coordination.

Does the Canadian Shield reduce earthquake risk in North Bay?

The Shield bedrock provides very firm foundation conditions (Class A) with minimal amplification. However, most of urban North Bay sits on glacial lake deposits overlying the Shield. The impedance contrast between soft clay and hard rock actually increases amplification at certain frequencies. The depth of the soil column controls the dominant site period.

Can a microzonation study be used for a single building design?

Yes. Single-building microzonation provides the site-specific design spectrum required for NBCC 2020 dynamic analysis. The structural engineer receives acceleration time histories compatible with the site class, fundamental period, and target spectrum. This replaces the default site class assumption with measured data, often reducing foundation costs on rock sites.

Location and service area

We serve projects in North Bay Ontario and surrounding areas.

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