A tiny earthquake to wake everybody up. The Attica earthquake of 1929 defines the seismic hazard for the region. Probably identical to the Cornwall earthquake of 1944, these earthquakes should be considered 'common' for seismic zones in this area. Certainly, I consider this to be the 'average' scenario for the Toronto earthquake.
We had an M5.0 and M5.4 in the Cleveland area, and all of these zones are identical from a rock mechanics point of view. That is why Toronto is #5 in seismic hazard, and #1 in ignorance!