Tuesday 27 May 2014

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...

Natural Resources Canada recorded a Magnitude 4.6 Earthquake...

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

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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