Abstract

Ottawa ranks third among Canadian urban areas in terms of seismic risk. Scenario ShakeMaps are generated for the Ottawa region to study the expected ground‐shaking intensity distribution patterns for input to damage and risk studies. Variability in near‐surface geology plays an important role in earthquake ground shaking in the region. The quarter‐wavelength method is used to generate frequency‐dependent amplification functions for typical generic soil profiles across the city, using shear‐wave velocity and depth‐to‐bedrock data from ∼17,250 compiled soil profiles. The methodology is validated using the ground‐motion and “Did You Feel It” records from the 2010 M 5 Val‐des‐Bois earthquake, which occurred 60 km from Ottawa. It is noted that the calculated amplifications for typical Ottawa soil profiles are often greater than generic National Earthquake Hazards Reduction Program factors as applied in building code applications.

For a scenario earthquake corresponding to the National Building Code of Canada probability level of forumla, expected modified Mercalli intensity values in soft‐soil areas of Ottawa would be near 7 on average. The impact of event location on expected ground motions and intensities was tested by considering the occurrence of a scenario earthquake (a given magnitude event) at various locations in the region. The results of this study may be used as input to seismic risk studies for Ottawa.

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