On June 23 at 1:41 PM a magnitude 5.0 earthquake occurred approximately 50km north of Ottawa.1 Four minutes later the quake was felt in the Waterloo area: students in several buildings felt the effects, some mistaking them for construction. Effects were less mild in Ottawa, with large portions of the government interrupted until building integrity checks could be performed.2
Unlike the (geologically) young faults around the Pacific rim, the western Quebec seismic zone consists mostly of old faults far from a plate boundary, which makes earthquake activity hard to predict. According to the U.S. Geological Survey the best predictors of seismic activity in the area are the earthquakes themselves.3
by Charlie Chaplain
2 Ottawa Citizen, "Federal, city staff review quake response", link.