June 23, 2010 Earthquake: Val-Des-Bois, Gracefield, Quebec, Canada

Slight damage at Gracefield, Quebec and landslides occurred in the epicentral area. Felt (VI) at Val-des-Bois and (V) at Fort-Coulonge, Maniwaki, Papineauville, Saint Andre Avellin, Sainte-Julienne and Thurso. Also felt (V) at Buckingham, Constance Bay and Rockland, Ontario. Felt in much of southern Ontario and Quebec and in parts of New Brunswick and Nova Scotia. Felt (IV) in the Massena area, New York. Felt in much of Connecticut, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island and Vermont and in parts of Delaware, District of Columbia, Illinois, Indiana, Kentucky, Maine, Maryland, Missouri, Virginia, West Virginia and Wisconsin.

The June 23, 2010 Val-des-Bois, Quebec earthquake occurred at 1:42 pm local (eastern) time 56 km (35 miles) north of Ottawa, Ontario, Canada's capital city. The preliminary estimate of magnitude (M) is 5.0, at a depth of 16 km (10 miles). These estimates may change as more data become available.

This earthquake occurred near the southern edge of the Western Quebec Seismic Zone. Earthquakes within this zone are mostly small. They tend to cluster in a wide area that is slightly elongated northwest-southeast. Historically, earthquakes in the Western Quebec Seismic Zone have caused damage roughly once a decade. Roughly ten events each year are felt in the region but are generally too small to cause damage. Still smaller earthquakes are much more common. The largest earthquakes known in this part of Canada occurred in 1935 (M6.1), about 250 km (150 miles) to the northwest of the Val-des-Bois event, and in 1732 (M6.2), about 150 km (100 miles) to the east of the earthquake. The 1732 earthquake caused significant damage in Montreal. In 1944, the Cornwall-Massena earthquake (M5.8) caused damage near the junction of Ontario, Quebec, and New York State.

Earthquakes the size of the Val-des-Bois event are uncommon east of the Rockies, but many have occurred since the arrival of European settlers three centuries ago. In eastern North America and geologically similar regions worldwide, M5.0 to M5.5 earthquakes typically cause light to moderate damage out to a few tens of kilometers (miles) from the epicenter, depending on the number of people and type of buildings near the epicenter. Typically these earthquakes are felt hundreds of kilometers (miles) away. Earthquakes of this size and depth are unlikely to rupture the Earth's surface, although exceptions are known.

The main faults near this earthquake zone trend northwest. These faults form the Ottawa graben and were most active several hundred million years ago. Some of the faults of the graben have been reactivated one or more times since then. The initial focal mechanism of the Val-des-Bois earthquake suggests reverse faulting on a fault trending southeast-northwest. However, the size and depth of the earthquake make it uncertain whether the causative fault can be identified.

Felt Reports

Slight damage at Gracefield, Quebec and landslides

occurred in the epicentral area. Felt (VI) at Val-des-

Bois and (V) at Fort-Coulonge, Maniwaki,

Papineauville, Saint Andre Avellin, Sainte-Julienne

and Thurso. Also felt (V) at Buckingham, Constance Bay

and Rockland, Ontario. Felt in much of southern

Ontario and Quebec and in parts of New Brunswick and

Nova Scotia. Felt (IV) in the Massena area, New York.

Felt in much of Connecticut, Massachusetts, Michigan,

New Hampshire, New Jersey, New York, Ohio,

Pennsylvania, Rhode Island and Vermont and in parts of

Delaware, District of Columbia, Illinois, Indiana,

Kentucky, Maine, Maryland, Missouri, Virginia, West

Virginia and Wisconsin.

Tectonic Summary

The June 23, 2010 Ontario-Quebec border region earthquake occurred at 1:42 pm local (eastern) time about 60 km (38 miles) north of Ottawa, Ontario, Canada's capital city. The preliminary estimate of magnitude (M) is 5.0, at a depth of roughly 19 km (12 miles). These estimates may change as more data becomes available.

This earthquake occurred near the southern edge of the Western Quebec Seismic Zone. Earthquakes within this zone are mostly small. They tend to cluster in a wide area that is slightly elongated northwest-southeast. Historically, earthquakes in the Western Quebec Seismic Zone have caused damage roughly once a decade. Three or four smaller events each year are felt in the region but are generally too small to cause damage. The largest earthquakes known in this part of Canada occurred in 1935 (M6.1), about 250 km (150 miles) to the northwest of todays event, and in 1732 (M6.2), about 150 km (100 miles) to the east. The 1732 earthquake caused significant damage in Montreal.

(above from reference #1053)

The June 23, 2010 Val-des-Bois, Quebec earthquake was the one of the largest recent events in eastern Canada. This earthquake produced the strongest shaking ever felt in Ottawa. It was felt widely in Ontario and Quebec, and it was also felt into the United States as far as Kentucky. Some damage occurred in the epicentral region. (reference #11312)

CBC News Canada, Thursday 24 June 2010. Quake damage shuts church, arena. A century-old church in Gracefield, Que., and an Ottawa arena are closed to the public after the two buildings were damaged in Wednesday's 5.0-magnitude earthquake. Gracefield initially called for emergency help due to the damage, which also included a collapsed ceiling at its community centre. The shaking knocked down tombstones and loosened lumber and bolts on a local bridge, forcing the town to block access to the crossing. But it lifted the state of emergency on Thursday after engineers determined most of the village's buildings remain structurally sound. Other damage in the region included a landslide that rendered a section of Highway 307 in Quebec impassable and a bridge's collapse into a river near the same highway, close to Bowman, Que. At least 30 Ottawa schools were damaged, but only four have possible structural problems and none has been closed. Several other municipal buildings are also damaged, including one fire station near the Barbara Ann Scott Arena that ended up with a crack in its wall. (reference #8035)