Earthquake hits Ottawa, Canada

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Saturday, February 25, 2006

Map showing quake location from USGS Quake Center

"An earthquake struck Ottawa, Canada at approximately 8:45 p.m. Eastern Standard Time on February 24, 2006." said one area resident. Natural Resources Canada, however, says the earthquake of 4.5 magnitude struck Western Quebec on February 25 at approximately 1:39 UTC (Coordinated Universal Time) which is effectively GMT (Greenwich Mean Time). (Earthquakes are generally listed in UTC time to ensure an absolute and consistent basis of when they occurred.) This may have been felt several hundred kilometres away.

Located North of Thurso

According to the Canadian Press the earthquake was centred north of Thurso, Quebec, "approximately 45 kilometres east-northeast of Ottawa, said John Adams, a seismologist with Natural Resources Canada." Witness reports state somewhat violent shaking with little or no property or personal damage. "It started as a rumble, then shaking... the whole house was shaking and the glasses were rattling," said Jeff Thiessen, a resident of Manor Park. One Ottawa resident said "the ground shook for about 30 seconds and was felt by residents near the city center." There were no immediate reports of injuries or damage to property.

According to the U.S. Geological Survey (USGS) "A magnitude 4.0 eastern earthquake typically can be felt at many places as far as 100 km (60 mi) from where it occurred, and it infrequently causes damage near its source."

Follow-up reports indicate that rumbles could be felt as far as Kingston, Ontario, Montreal, Quebec and New York. The Canadian Geological Survey stated 14 seismometer stations revising a magnitude of 4.5 from 2.99 on the Richter Scale. The USGS pronounced it to be a 4.0 tremor.

Seismic region far from plate boundaries

The Edinburgh earth observatory also demonstrates that this earthquake, with a reported depth of approx. 18 km, occurred near the North American Plate. However, according to USGS, "the Western Quebec seismic zone is far from the nearest plate boundaries, which are in the center of the Atlantic Ocean and in the Caribbean Sea." Because the area has many faults, some smaller, deeper and some not yet detected, few, if any, earthquakes can be linked to named faults. Furthermore USGS says that the best guide to predicting earthquakes of the sort, in the Western Quebec seismic zone, is actually having the earthquake.

Pattern of quakes in the area

The Ontario region has not encountered a major earthquake since October 1990 when a 5.0 occurred in Eastern Ontario. The Ottawa Sun reports this is the third significant tremor in the region for 2006. The two largest damaging earthquakes for this region occurred in "1935 (magnitude 6.1) at the northwestern end of the seismic zone, and in 1732 (magnitude 6.2) 450 km (280 mi) away at the southeastern end of the zone where it caused significant damage in Montreal." Smaller earthquakes, such as this, are felt about three to four times a year.