Magnitude 3.8 Earthquake beneath the St Lawrence River Estuary.

Natural Resources Canada recorded a Magnitude 3.8 Earthquake beneath the St Lawrence River Estuary in Quebec, slightly before 5.35 pm local time (slightly before 9.35 pm GMT) on Monday 26 May 2014. There are no reports of any damage or injuries associated with this event, though it was felt in the city of Baie-Comeau on the north side of the estuary.

The approximate location of the 26 May 2014 St Lawrence River Estuary. Google Maps.

The Lower St. Lawrence Seismic Zone lies largely beneath the St. Lawrence River Estuary. Small quakes are very common here, averaging roughly one per week, but larger quakes are all but unheard of, with only two quakes in excess on a Magnitude 5.0 ever being recorded. The Seismic Zone is thought to be connected to a graben-structure (area of tectonic plate expansion) beneath the river, the formation of which relates to the opening of the Iapetus Ocean in the late Proterozoic to early Paleozoic, which has become reactivated during the breakup of Pangea and the formation of the Atlantic Ocean, around 150 million years ago. In a graben structure the Earth's crust is stretched and becomes thin, then faulting occurs allowing the central part to sink.

Witness reports can help geologists to understand the processes going on in Earthquakes and the structures in the rocks that cause them. If you felt this quake you can report it to Natural Resources Canada here.

See also...

 Magnitude 4.6 Earthquake beneath the St Lawrence River Estuary.

Natural Resources Canada recorded a Magnitude 4.6 Earthquake...

 Quebec Earthquake felt in New York, Vermont.

A Magnitude 4.4 Earthquake occurred at a depth of 9 km in southern...

 Quebec Earthquake, 27 August 2011.

At about 2.25 am on Saturday 27 August 2011, the Canadian province of Quebec suffered a minor earthquake. The quake measured 3.0 on the Richter Scale and occurred at a depth of about 12.8 km, just about large and shallow enough to have been felt, but unlikely to have caused any damage. The epicenter of the quake was about 40 km to the east of Quebec City.

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Magnitude 4.6 Earthquake beneath the St Lawrence River Estuary.

Natural Resources Canada recorded a Magnitude 4.6 Earthquake slightly before 10.50 am local time (slightly before 2.50 pm GMT) on Saturday 21 September 2013. This was a moderately large quake, and was felt on both sides of the estuary, though there are no reports of any damage or casualties.

The approximate location of the 21 September 2013 St Lawrence River Estuary Earthquake. Google Maps.

The Lower St. Lawrence Seismic Zone lies largely beneath the St. Lawrence River Estuary. Small quakes are very common here, averaging roughly one per week, but larger quakes are all but unheard of, with only two quakes in excess on a Magnitude 5.0 ever being recorded. The Seismic Zone is thought to be connected to a graben-structure (area of tectonic plate expansion) beneath the river, the formation of which relates to the opening of the Iapetus Ocean in the late Proterozoic to early Paleozoic, which has become reactivated during the breakup of Pangea and the formation of the Atlantic Ocean, around 150 million years ago. In a graben structure the Earth's crust is stretched and becomes thin, then faulting occurs allowing the central part to sink.

Witness reports can help geologists to understand the processes going on in Earthquakes and the structures in the rocks that cause them. If you felt this quake you can report it to Natural Resources Canada here.

See also Earthquake shakes Cleveland, Ohio, Earthquake under Maine shakes New England, Earthquake in Labrador, Canada and Quebec Earthquake, 27 August 2011.

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Earthquake in Labrador, Canada.

On Sunday 8 July 2012, slightly before 8.15 pm local time (slightly before 11.15 pm, GMT), an Earthquake struck in eastern Labrador, roughly 146 km south of Happy Valley, according to the United States Geological Survey, who measured the quake as 4.4 on the Richter Scale at a depth of 18 km. An Earthquake of this size is highly unlikely to have caused any damage or casualties, but would have been felt as severe shaking by anybody in the area.

The location of the 8 July 2012 quake. USGS.

Earthquakes in Labrador are extremely rare, making the cause of such quakes hard to determine. This is largest quake in the area since 1962. Eastern Canada is a long way from any active plate margins, the nearest being the Mid Atlantic Rift Zone, which runs through Iceland far to the east, and the subductive zone along the west coast of North America, far to the west. 

There are, however, a number of areas of tectonic stress in eastern Canada, one of which, the Lower St. Lawrence Seismic Zone, runs beneath the St Lawrence River, roughly 200 km southeast of the epicenter of the 8 July quake. This is hard to study directly, but seismic studies, which are based upon monitoring the way waves of energy from known quakes travel through the rocks below the region, enabling scientists to build a three dimensional image of the geological structure beneath the river in a similar way to sonar, suggest that this is caused by the reactivation of an ancient rift zone associated with the opening of the Iapetus Ocean in the Late Proterozoic to Early Paleozoic (i.e. roughly 500 million years ago).

Information from witnesses who felt quakes is extremely useful to scientists studying seismic activity. If you felt this Earthquake you can report it to Natural Resources Canada here.

See also Oklahoma shaken by Earthquake on Christmas Day, The dangers of a modern Laki style eruption in Iceland, Earthquake off the coast of Vancouver Island, Quebec Earthquake, 27 August 2011 and Earthquakes on Sciency Thoughts YouTube.

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