Tsunami warning after 7.7 Canada earthquake .................

A MAJOR 7.7 magnitude earthquake has rocked the Queen Charlotte Islands off the west coast of Canada with no immediate reports of damage.

The epicentre of the tremor, which occurred at 8.04pm on Saturday (1404 AEDT Sunday) was located 139km south of the town of Masset, the US Geological Survey said.

The Pacific Tsunami Warning Center said there was no "destructive widespread tsunami threat" at this time.

However, the regional West Coast-Alaska Tsunami Warning Center issued a regional warning for coasts located near the epicentre of the earthquake.

"A 7.7 is a big, hefty earthquake. It's not something you can ignore," Gerard Fryer, senior geophysicist at the Pacific Tsunami Warning Center told CNN International.

He explained that the latest tremor had occurred partly under an island, but mostly under shallow water.

"I think we have to be thankful it happened where it did," Fryer said.

"If that were a heavily populated area, it would have caused significant damage.

"It definitely would have done significant damage if it had been under a city."

The Globe and Mail newspaper reported the quake was felt in Haida Gwaii Island and across a swathe of north and central British Columbia including Prince Rupert, Quesnel and Houston, with no immediate reports of damage.

The US Coast Guard in Alaska was trying to warn everyone with a boat on the water to prepare for a potential tsunami, the report said.

The Canadian paper also quoted Lieutenant Bernard Auth of the Juneau Command Center as saying that the US Coast Guard was also working with local authorities to alert people in coastal towns to take precautions.

The earthquake reading was based on the open-ended Moment Magnitude scale used by US seismologists, which measures the area of the fault that ruptured and the total energy released.