3 earthquakes detected within minutes off B.C. coast

Three earthquakes registering between 4.5 and 5.6 magnitude were detected off the coast of B.C. on Friday morning.

The tremors, classified as aftershocks to a Wednesday quake, struck within minutes of each other to the south of Haida Gwaii on Friday — one at 5:51 a.m. PT, another 5:58 a.m. and the third at 6:02 a.m. 

The first was detected with a preliminary magnitude of 4.5, according to the U.S. Geological Survey (USGS). The agency said the second quake had a preliminary magnitude of 5.6 and the third measured 4.6.

A tweet from Emergency Info B.C. said there is no tsunami threat to the province. USGS said no damage is expected.

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More aftershocks expected: USGS

An earthquake measuring 6.2 magnitude was registered in the same area on Wednesday night. Haida Gwaii is an archipelago about 50 kilometres off the B.C. coast.

Alison Bird, a seismologist with the Pacific Geoscience Centre near Victoria, said the centre is working to determine if the latest tremors are part of a swarm sequence — an outbreak of seismic activity, which Bird said is common off the B.C. coast.

"It often has a sudden flurry of activity where you get 100 earthquakes within a week-and-a-half period,'' she said. "They're a bit of a nuisance.''

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On Thursday, Southern California and parts of Nevada experienced a 6.4 magnitude earthquake, the most powerful to hit the state in 20 years. That quake occurred in the Mojave Desert, near the city of Ridgecrest, 320 kilometres northeast of Los Angeles and was followed by dozens of aftershocks.

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A magnitude 5.4 quake at 4:07 a.m. on Friday is so far the strongest aftershock of Thursday's jolt in California, and was felt widely.

Seismologists had said there was an 80 per cent probability of an aftershock of that strength.

Paul Caruso, a geophysicist and duty seismologist with the USGS, said the quakes off the Canadian coast this week are not linked to that in California.

"The California quake was very far away, and those quakes were inland and these quakes are in the ocean … there's no relationship," said Caruso, speaking by phone Friday morning.

The geophysicist said aftershocks are "common" after a quake like the one B.C. saw Wednesday.

"We're probably going to see aftershocks continuing for a week or two," he said.