BREAKING NEWS: Magnitude-6.7 earthquake rattles Vancouver Island

VICTORIA - A magnitude-6.7 earthquake has struck off the coast of Vancouver Island.

The United States Geological Survey recorded the quake at 12:41 p.m. local time.

A map on the geological survey's website puts the epicentre just off the west coast of Vancouver Island, south of Port Hardy.

The quake was recorded at a depth of 80 kilometres

The Pacific Tsunami Warning Centre has posted an information bulletin that says no tsunami is expected.


Many regions of British Columbia were shaken Friday afternoon by a magnitude 6.7 earthquake that struck off the coast of Vancouver Island.



Many regions of British Columbia were shaken Friday afternoon by a magnitude 6.4 earthquake that struck off the coast of Vancouver Island.


While no tsunami warning was triggered by the quake, a geophysicist with the U.S. Geological Survey said damage is possible in many B.C. regions.

"It's been felt pretty widely — we have reports of it being felt in Vancouver, Victoria and even in Seattle," said Paul Caruso. "In the north, it's been felt as far as Port Hardy.

"We don't have any reports of damage yet, but we would probably expect to see some damage — especially for anybody living on the central-west coast of Vancouver Island."

Caruso said the earthquake, which occurred just after 12:40 p.m. local time, was centred about 280 kilometres west of Vancouver and about 25 kilometres beneath the seabed.

He said people in Campbell River, on Vancouver Island, likely would have felt the quake also because it was centred about 135 kilometres west of that city.

No tsunami warning was issued, Caruso said, because "the magnitude of the quake isn't big enough to generate a tsunami by itself."

Regardless, he said some residents will be directly effected by the earthquake.

"People might experience — if they're near the epicentre on the west coast of the island — they might have some damage, with things falling off shelves and cracked foundations," Caruso said. "As far as the mainland, we would probably expect to see very minor damage. People would probably see their chandeliers swinging back and forth and feeling a little bit of shaking."

There were no immediate signs of damage in downtown Vancouver, although lights swayed for a half-minute when the quake struck.

The earthquake shook buildings in the tiny Vancouver Island community of Zeballos, but there appeared to be no damage and there were no injuries.

The power went down but came back quickly, said Arlene Coburn, a 38-year resident of the remote west coast community.

Coburn was at the school when the earthquake hit. She said it felt like the whole building was going to topple over, but nothing fell off the walls.

"One big one, and a little tremor, and that was it," she said. "It gave (the school) a good sway."

The 60 or so children who attend the Zeballos Elementary Secondary School were ushered out and across a bridge, a measure used when there's a threat of a tsunami, said Coburn, a part-time janitor at the school.

Arlene's husband, Geoff, said there were no injuries and no damage as far as he knew in the community of about 200 people. "There was no cause for panic," said Geoff.

Brent Ward, a professor in Simon Fraser University's department of earth sciences, said people were more likely to feel the quake if they were in tall buildings because of the sway.

He said it was one of the biggest quakes experienced on the west coast, with the last one in Washington State.

"Six point seven (the quake's originally estimated magnitude) is nothing to sneeze at," he said. "You think of the earthquake in Haiti and it was about the same but it was shallow."

He said the quake likely originated in stress built up due to the oceanic Juan de Fuca plate subducting under the North American plate.

The quake created a slight rattling as far away as Seattle, Washington, but police in the U.S. city said there were no reports of damage. The list of cities where the quake was felt includes San Francisco and Edmonton.

In an interview with the Cowichan Valley Citizen in February, Alison Bird, a seismologist for Natural Resources Canada, said earthquakes happen very frequently in the region, noting that in 2010 alone more than 3,000 minor earthquakes were recorded in Western Canada.

"We have smallish earthquakes very regularly," she said. "It's a fairly routine event."

And according to the Victoria Times Colonist, the largest quake to hit the region in recent memory was the 6.8-magnitude Nisqually earthquake southwest of Seattle, Washington in February 2001.

Only the ninth earthquake in this area in 125 years measuring over magnitude 6, it cracked the dome of the Capitol building in Olympia, Washington, damaged the control tower at Sea-Tac airport and shook bricks off chimneys in Victoria.

1946 Vancouver Island earthquake

1946 Vancouver Island earthquake

Date June 23, 1946 (1946-06-23)

Magnitude 7.3 Mw

Depth approx. 20 kilometres (12 mi)

Countries or regions Canada

United States

Max. intensity VIII - Destructive

Casualties 2 killed[1]

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.[2] The main shock epicenter occurred in the Forbidden Plateau area northwest of Courtenay. While most of the large earthquakes in the Vancouver area occur at tectonic plate boundaries, the 1946 Vancouver Island earthquake was a crustal event.[3] Shaking was felt from Portland, Oregon to Prince Rupert, British Columbia. The earthquake is remembered as one of the most damaging earthquakes in the history of British Columbia. However, damage was restricted because there were no heavily populated areas near the epicenter, where the violent shaking occurred.

This earthquake is Canada's largest historic onshore earthquake.[2] However, the greatest earthquake in Canadian history recorded by seismometers was the 1949 Queen Charlotte earthquake, an interplate earthquake that occurred on the ocean bottom just off the rugged coast of Graham Island, which reached magnitude 8.1 on the moment magnitude scale.[4]

Contents

1 Background and tectonics

2 Damage and casualties

3 See also

4 References


Background and tectonics

The tectonics that caused the 1946 Vancouver Island earthquake are poorly known. No surface expression of the offset was noticed, most likely because the epicenter area is very remote and densely forested. A comprehensive examination and computer interpretation of seismic data from over 50 stations has shown that a possible explanation of the earthquake includes a strike-slip fault corresponding to the lengthy axis of Vancouver Island known as the Beaufort Range Fault.[5] A fault running across Vancouver Island, corresponding to the projection of the underwater Nootka Fault on the British Columbia Coast is also a possibility, but this is less likely to be true, because the earthquake should have given evidence of offsets along a series of highways that follows much of the eastern coastline of Vancouver Island, called Island Highway, and other roads between the Courtenay and Campbell Rivers. The estimated depth of the earthquake places it within the continental crust, not at the margin with the Cascadia subduction zone, and certainly not inside the subduction zone itself. Specifically, the earthquake's epicenter was positioned somewhere in the Forbidden Plateau region, located in central Vancouver Island.

Damage and casualties

Soil failure north of Campbell River on Kelsey Bay Highway.Though very destructive, the earthquake caused only two casualties: Jacob L. Kingston, aged 69, and Daniel Fidler, who was 50.[1] One of the two had a heart attack; the other drowned when his dinghy was swamped by a wave.

In Vancouver, damage consisted of lofty buildings oscillating violently, and a piece of masonry fell from the local railway station. In addition, within the city, at least one gas line cracked and several power outages occurred. Fires broke out in several chimneys, and at least one swing span bridge was fractured by the shaking. In the Hotel Vancouver, which housed the elderly and caught on fire, more than 500 war veterans' families fled the flames. One writer, George Finley, stated that the Lions' Gate Bridge "swayed like a leaf", coinciding with a "low, rumbling sound, like a deep growl."[1]

House failure in Comox by the 1946 Vancouver Island earthquake.The 1946 Vancouver Island earthquake demolished 75% of the chimneys in the communities of Cumberland, Union Bay, and Courtenay and caused extensive damage in Comox, Port Alberni, and Powell River, on the eastern side of the Strait of Georgia.[2] Some chimneys were fractured in Victoria, and people in Victoria and Vancouver experienced great fright, with some seen fleeing into the streets.[2]

Landslides created by the earthquake were common throughout Vancouver Island.[6] Land subsidence resulted from the earthquake, most commonly around shorelines on the Strait of Georgia.[6] This included the bottom of Deep Bay which sank between 2.7 m (9 ft) and 25.6 m (84 ft).[7] These measurements were reported by the Canadian Hydrographic Department.[7] Also, a 3-metre (9.8 ft) ground shift occurred on Read Island.[7] Ships throughout the region were affected, and those on board them during the earthquake described it as similar to having run over a sand bar or striking a rock.[6] Undersea power lines were destroyed in the long narrow Alberni Inlet and near the city of Powell River.[6] All lighthouse keepers in the surrounding area felt the earthquake, and experienced damages including shattered windows and smashed dishes.[6] A tsunami struck the west coast of Texada Island with two waves, the first was 2 metres (6 ft 7 in) high and the second 1 metre (3 ft 3 in) high.[6] The earthquake caused a landslide near Mount Colonel Foster. One fortunate occurrence allowed researchers afterward to review the effects of the earthquake: an aerial photographic survey of Vancouver Island had commenced in 1946, soon after the earthquake; these photographs were eventually studied by a geoscientist in the late 1970s.[6]

South of the Canada–United States border in Washington State, some chimneys fell at Eastsound and on Orcas Island and a concrete mill was damaged at Port Angeles.[7] In Seattle, some damage occurred on upper floors of tall buildings, and one bridge was damaged. The shock was strongly felt at Bellingham, Olympia, Raymond, and Tacoma.[7] The earthquake was powerful enough to knock the needle off a seismograph at the University of Washington, and was sustained for about a minute even in Seattle.

The earthquake caused somewhat astounding movement among structures, moving one 300-foot (91 m) wall about 35 feet (11 m) and caused one home to shift for 5 feet (1.5 m) off its foundation.[1] The total affected area in Canada and the United States was about 260,000 km2 (100,000 sq mi).[7]


List of earthquakes in Canada

List of earthquakes in the United States

List of deadly earthquakes since 1900

1918 Vancouver Island earthquake

1949 Queen Charlotte earthquake

References

1.^ a b c d "Damage Considerable In Coastal Area of Sunday Quake". Ellensburg Daily Record. June 24, 1946. http://news.google.com/newspapers?id=RE0KAAAAIBAJ&sjid=8UoDAAAAIBAJ&pg=4967,2345608&dq=1946+vancouver+island+earthquake. Retrieved January 6, 2009.

2.^ a b c d The M7.3 Vancouver Island Earthquake of 1946 Retrieved on 2008-06-11

3.^ 1946 Vancouver Island Earthquake Anniversary Retrieved on 2008-06-11

4.^ The Magnitude 8.1 Queen Charlotte Island Earthquake of August 22, 1949 Retrieved on 2008-06-11

5.^ W. F. Slawson; J. C. Savage (October 1979). "Geodetic deformation associated with the 1946 Vancouver Island, Canada, earthquake". Bulletin of the Seismology Association of America 69 (5): 1487–1496. http://bssa.geoscienceworld.org/cgi/content/abstract/69/5/1487.

6.^ a b c d e f g M Gunn, Angus (2008). Encyclopedia of Disasters. Westport, Connecticut: Greenwood Press. pp. 399. ISBN 978-0-313-34002-4. http://books.google.com/?id=4YzF-DT__aIC&pg=RA1-PA399&lpg=RA1-PA399&dq=1946+Vancouver+Island+earthquake.

7.^ a b c d e f "Washington: Earthquake History". USGS. 2008-07-16. http://earthquake.usgs.gov/regional/states/washington/history.php. Retrieved 2009-01-08.


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