The Charlevoix Seismic Zone is a seismically active area in the Charlevoix region of northeastern Quebec, Canada. It is also known as the Charlevoix-Kamouraska Seismic Zone because earthquakes occur in Kamouraska County where the land expression of the seismic zone is separated by the Saint Lawrence River. [1] Much seismic activity takes place under the river. [1]
In seismology, a seismic zone is an area of seismicity potentially sharing a common cause. It may also be a region on a map for which a common areal rate of seismicity is assumed for the purpose of calculating probabilistic ground motions. An obsolete definition is a region on a map in which a common level of seismic design is required.
Charlevoix is a cultural and natural region located in Quebec, on the north shore of the Saint Lawrence River as well as in the Laurentian Mountains area of the Canadian Shield. This dramatic landscape includes rolling terrain, fjords, headlands and bays; the region was designated a World Biosphere Reserve by UNESCO in 1989.
Quebec is one of the thirteen provinces and territories of Canada. It is bordered to the west by the province of Ontario and the bodies of water James Bay and Hudson Bay; to the north by Hudson Strait and Ungava Bay; to the east by the Gulf of Saint Lawrence and the province of Newfoundland and Labrador; and to the south by the province of New Brunswick and the U.S. states of Maine, New Hampshire, Vermont, and New York. It also shares maritime borders with Nunavut, Prince Edward Island, and Nova Scotia. Quebec is Canada's largest province by area and its second-largest administrative division; only the territory of Nunavut is larger. It is historically and politically considered to be part of Central Canada.
With over 200 small earthquakes occurring each year, the Charlevoix Seismic Zone is one of the most active seismic zones in Canada. Since 1663, five damaging earthquakes have occurred in the area, including a magnitude 7.3-7.9 event in 1663, a magnitude 7.0 event in 1791, a magnitude 6.0 event in 1860, a magnitude 6.5 event in 1870 and a magnitude 6.2 event in 1925. Because of these concerns, the Charlevoix Seismic Zone is considered to be a highly hazardous earthquake zone and it is comparable to those in British Columbia where earthquakes are due to movement of the Earth's tectonic plates. In contrast, the Charlevoix Seismic Zone lies in the interior of the North American Plate and its origin is not well known. [2]
An earthquake is the shaking of the surface of the Earth, resulting from the sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in size from those that are so weak that they cannot be felt to those violent enough to toss people around and destroy whole cities. The seismicity, or seismic activity, of an area is the frequency, type and size of earthquakes experienced over a period of time. The word tremor is also used for non-earthquake seismic rumbling.
The 1663 Charlevoix earthquake occurred on February 5 in New France, and was assessed to have a moment magnitude of between 7.3 and 7.9. The earthquake occurred at 5:30 p.m. local time and was estimated to have a maximum perceived intensity of X (Extreme) on the Mercalli intensity scale. The main shock epicentre is suggested to have occurred along the Saint Lawrence River, between the mouth of the Malbaie River on the north and the mouth of the Ouelle River on the south. A large portion of eastern North America felt the effects. Landslides and underwater sediment slumps were a primary characteristic of the event with much of the destruction occurring near the epicentral region of the St. Lawrence estuary and also in the area of the Saguenay Graben.
The 1925 Charlevoix–Kamouraska earthquake struck northeastern North America on February 28, reaching 6.2 on the moment magnitude scale. It was one of the most powerful measured in Canada in the 20th century, with a maximum perceived intensity of VIII (Severe) on the Mercalli intensity scale at its epicentre in the area of Charlevoix-Kamouraska along the Saint Lawrence River near île aux Lièvres and not greater than VI (Strong) in the United States. The quake was felt in Quebec, Shawinigan, Montreal, as far south as Virginia, and as far west as the Mississippi River.
