A magnitude 6.4 earthquake struck 175 miles west of Vancouver

Vancouver

Vancouver is a coastal seaport city on the mainland of British Columbia, Canada. It is the hub of Greater Vancouver, which, with over 2.3 million residents, is the third most populous metropolitan area in the country,...

 at 12:41 p.m. local time on Sept 9, 2011, 23 km (14.3 miles) deep. It lasted 20-30 seconds. No damage was reported. Many aftershocks occurred, including a magnitude 4.9 tremor on the same day, without any damages.

Geology

The magnitude 6.4 earthquake occurred on a continental

Continental crust

The continental crust is the layer of igneous, sedimentary, and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial due to more felsic, or granitic, bulk composition, which lies in...

 section of transform fault

Transform fault

A transform fault or transform boundary, also known as conservative plate boundary since these faults neither create nor destroy lithosphere, is a type of fault whose relative motion is predominantly horizontal in either sinistral or dextral direction. Furthermore, transform faults end abruptly...

 line in Vancouver Island

Vancouver Island

Vancouver Island is a large island in British Columbia, Canada. It is one of several North American locations named after George Vancouver, the British Royal Navy officer who explored the Pacific Northwest coast of North America between 1791 and 1794...

, near to but not directly over the northern Cascadia subduction zone

Cascadia subduction zone

The Cascadia subduction zone is a subduction zone, a type of convergent plate boundary that stretches from northern Vancouver Island to northern California. It is a very long sloping fault that separates the Juan de Fuca and North America plates.New ocean floor is being created offshore of...

, the plate boundary between the eastern flank of the Juan de Fuca Plate

Juan de Fuca Plate

The Juan de Fuca Plate, named after the explorer of the same name, is a tectonic plate, generated from the Juan de Fuca Ridge, and subducting under the northerly portion of the western side of the North American Plate at the Cascadia subduction zone...

 and the western North American Plate

North American Plate

The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...

. The earthquake was the strongest to hit the region since a magnitude 6.6 tremor in November, 2004.

See also

• 2010 Eureka earthquake
• 2007–2008 Nazko earthquakes
• 2001 Nisqually earthquake
• 1949 Queen Charlotte earthquake
  1949 Queen Charlotte earthquake
  The Queen Charlotte Islands earthquake of 1949 was a magnitude 8.1 interplate earthquake that struck the sparsely populated Queen Charlotte Islands and the Pacific Northwest coast on August 22, 1949. It is one of the world's greatest earthquakes. The main shock epicenter began in the ocean bottom...
  
  
• 1946 Vancouver Island earthquake
  1946 Vancouver Island earthquake
  The 1946 Vancouver Island earthquake was a 7.3 magnitude earthquake that struck Vancouver Island, on the Coast of British Columbia, Canada, at 10:15 a.m. on Sunday, June 23, 1946. The main shock epicenter occurred in the Forbidden Plateau area northwest of Courtenay...
  
  
• 1918 Vancouver Island earthquake
  1918 Vancouver Island earthquake
  The 1918 Vancouver Island earthquake was a large earthquake that struck British Columbia, Canada at 12:41 a.m. on Friday, December 6, 1918.This was most likely a strike-slip earthquake, with epicenter near the west coast of Vancouver Island....
  
  
• 1700 Cascadia earthquake