| Résumé | (disponible en anglais seulement)
Based on its earthquake hazard and population, the seismic risk of the OttawaGatineau region ("the region '') ranks third in Canadian urban areas. As part of a
research activity that aims at defining microseismic zoning for the region, the historical earthquake damage was examined The available written documents were searched for iriformation on damage related to some eighteen events that were most likely
to have had some impact in the region. It was found that between years 1830 and 2008, thirteen of these earthquakes reached or exceeded the Modified Mercalli Intensity (MMI) V level (fallen smalt abjects). Being located within the Western Quebec
Seismic Zone, the region was subjected to some moderate earthquakes (magnitude between 5.0 and 6.2) at less than 300 km epicentral distance. The local earthquakes of 1856, 1861, 1908, 1909, 1913, 1914, 1917, 1924, 1933, 1935, 1944 and 1983 Jal! in
that category. More distant earthquakes had some impact in Ottawa in 1870, 1924 and 1925 (epicenters in the Charlevoix Seismic Zone at about 450-525 km epicentral distance), in 1929 (Attica, N Y. at about 350 km distance) and in 1988 (Saguenay region
at about 470 km distance). The impact of these earthquakes in the Ottawa-Gatineau region was assembled in a database. For each earthquake, the database provides a description of damage together with ifs geographic coordinates, ifs corresponding MMI
and the supporting document as scanned images. Historically, certain wards sustained higher levels of ground motions due to moderate to large earthquakes.We found that the 10-50 m thick basin centered on the Museum of Nature had most instances of MMI
VI and VIL In contrast, areas with thin veneer of unconsolidateddeposits, such as the Parliament occurrences of damage. Since most earthquakes have occurred in the first half of the 20th century when Ottawa only occupied a small proportion of the
current urban area, it is uncertain if the areas with most occurrences of damage present the highest risk for future earthquakes. Knowledge of these more hazardous areas, such as the basin centered on the Museum of Nature, is of importance for land
use planning and emergency preparedness.Hill and the Hull ward of Gatineau had almost no occurrences of damage. Since most earthquakes have occurred in the first half of the 20th century when Ottawa only occupied a small proportion of the current
urban area, it is uncertain if the areas with most occurrences of damage present the highest risk for future earthquakes. Knowledge of these more hazardous areas, such as the basin centered on the Museum of Nature, is of importance for land use
planning and emergency preparedness. |