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Seismic Microzonation of the Greater Montréal Area
16/01/2012, page 1
Prof. Luc Chouinard
Department of Civil enginering and Applied [email protected]
Front steps of the Montreal East City Hall after the Saguenay earthuake (11/25/1988, Ms=6)
SEISMIC EFFECTS
Surface rupture
Slides
Amplification due to
topography Rock slides
Site
Amplification
due to soil
Liquefaction
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SEISMIC HAZARDS IN QUEBEC LARGE SMALL
Every 100 years on average…
4 ≤ M < 5 40 earthqaukes
5 ≤ M < 6 4 earthquakes
M ≥ 6 1 earthquake
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D’après Séisme Canada
RECENT SEISMIC ACTIVITY
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(Source :Adams, 2011)
SEISMIC ACTIVITY CLOSE TO MONTREAL
�March 23, 1897 - I =VI
IMM=VI General alert, moderate amount fo
damages to buildings and non-structural elements
IMM=VII Considerable damage to poorly built or
poorly designed buildings.
IMM=VIII General panic, considerable damage to
general building stock and non-structural elements.
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�March 23, 1897 - IMM=VI
� November, 1893 - IMM=VI
� September 16, 1816 - IMM=VI
� September 9, 1816 - IMM=VIII
� September, 16 1732 IMM=VIII
Widely felt
More than 300 houses damaged
(Source :National Earthquake Hazard Program, Ottawa, Canada)
SEISMIC ACTIVITY CLOSE TO MONTREAL
Damages of
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(Source :National Earthquake Hazard Program, Ottawa, Canada)
Damages of M$ in 1944
AMPLIFICATION OF SEISMIC WAVES DUE TO SOIL DEPOSITS
0.15g
0.17g
0.035g
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M6.6 Mexico earthquake (1985)
Attenuation with distance
Soil amplification
LOCAL SITE AMPLIFICATION FROM SOIL DEPOSITS
Hôtel de ville
de Montréal-Est
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Source: Tinawi et al. (1988) et CGC
Distance > 300km from epicenter
17m of clay at the site
Facade was in a poor state
USING MICROZONATION
Identify within the most critical zones:
- Critical infrastructures (hospitals, schools, fire stations , etc..)
- Critical lifelines (bridges, tunnels, water supply, etc.)
- Industrial sites
- Vulnerability of buildings
Develop earthquake scenarios to estimate :
- Damages to buildings
- Economic losees
- Societal consequences
Better understanding of hazards :
- New constructions
- Retrofit of existing structures
MICROZONATIONS
Identification of seismic amplification zones
- NBCC 2005 (2010) classification (Vs30)
- Others (e.g. Vs + F0)
Identification of potential soil instability
- Liquefaction
- Slopes
Input to ShakeMaps
- Scénario mode
- Operational mode
- Zones most affected during an earthquake
- Identification of potential damage to guide inspections and interventions
• Soil types and properties
• Soil response
– Amplification
– Liquefaction
– Slope stability
INPUTS FOR THE MICROZONATION
• Types of deposits
– Surface geology map
– Borings (~ 20,000 to bedrock)
– Detailed borings with soil layers (~ 2,000)
SOIL TYPE
– Detailed borings with soil layers (~ 2,000)
• Geotechnical properties
– SPT
– Vs (shear wave velocity)
– F0 (fundamental frequency)
SURFACE GEOLOGY MAP
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LAND USE
De
la C
omm
une
Nor
te-D
ame
Vig
er
Ren
é Lé
vesq
ue
Ste
-Cat
herin
e
De
Mai
sonn
euve
Ont
ario
She
rbro
okeCross-sections (~ Old-Montreal)
De
la C
omm
une
Vig
er
( ~ 20,000 borings).
Depth to bedrock
SOFT SOIL DEPOSITS
16 décembre 2002
3D soft deposits model (~ 2000 boreholes)
SOIL PROPERTIES: HVSR and F0
Measurements (10 min)-Avoid sources of large vibrations (heavy traffic industrial sites)-Avoid windy and rainy days
Ambient noise measurementAmbient noise measurement
Total number of sites over a 4 year period~ 1500 sites)
SOIL PROPERTIES: HVSR and F0
McGill processing software : Ground Ambient Noise Analysis
SPCRATIO
> 21
Surface depositsSurface depositsDepth to Depth to bedrockbedrock ff00
30-35mSABLE
ARGILE
Glaciaire
> 23
CorrelationsCorrelations
(Prest & Hode-Keyser, 1982)