February 5, 1663 Earthquake: St Lawrence Valley, Canada

This procedure suggests that the 1663 earthquake had a moment magnitude between 7.3 and 7.7. A different way to estimate the magnitude of the 1663 earthquake is to use the size of the Charlevoix Seismic Zone. The zone is about 45 miles (72 kilometers) long with an activity rate of a few earthquakes per week, and the length of this seismic zone probably reflects the length of the fault on which the 1663 earthquake slip took place. Modern earthquakes with a fault length of 45 miles or 72 kilometers have moment magnitudes between 7.3 and 7.6. Based on these numbers, a best estimate of the moment magnitude of the 1663 is about 7.5. This makes the 1663 earthquake comparable to the largest of the earthquakes that took place in the New Madrid, Missouri, area in 1811–1812. The New Madrid earthquakes are considered some of the largest earthquakes to have taken place in any stable continental region worldwide. (reference #13657)