Ottawa ranks third among Canadian urban areas in terms of seismic risk. Variability in near surface geology plays an important role in earthquake ground shaking in the region. Scenario ShakeMaps are generated for the Ottawa region to study the expected ground-shaking intensity distribution patterns, for input to damage and risk studies. The quarter wavelength method is used to generate frequency-dependent amplification functions for typical generic soil profiles for National Earthquake Hazard Reduction Program (NEHRP) soil classes using recent data from -17250 soil profiles. The methodology and amplifications are validated using the ground motion and “Did You Feel It” records from the 2010 M5 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 “NEHRP factors” as applied in building code applications.
For a scenario corresponding to ground motions specified by the National Building Code of Canada (NBCC) for a probability level of 2%/50 years, expected Modified Mercalli Intensity (MMI) values in soft-soil areas of Ottawa would be near 7. The impact of event location on expected ground motions and intensities was tested by considering the occurrence of a scenario (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
