VANCOUVER // A magnitude 7.7 earthquake struck off the coast of western Canada last night and a tsunami warning was issued, authorities said. There were no immediate reports of damage. The US Geological Survey in Colorado said the earthquake hit the Queen Charlotte Islands on Saturday evening and was centred 155 kilometres south of Masset, British Columbia. The National Weather Service issued a tsunami warning for coastal areas of British Columbia and southern Alaska. The USGS said the 7.7-magnitude tremor shook the area and was followed by a 5.8 magnitude aftershock several minutes later. The US Coast Guard in Alaska said it was trying to warn everyone with a boat on the water to prepare for a potential tsunami. Lt Bernard Auth of the Juneau Command Center said the Coastguard was also working with local authorities to alert people in coastal towns to take precautions. The earthquake occurred 40 kilometres south of Sandspit, British Columbia on the Haida Gwaii archipelago, formerly known as the Queen Charlotte Islands. Port Clements Golden Spruce hotel operator Urs Thomas said there was no warning before everything began moving inside and outside the hotel. He said it last about three minutes. "It was a pretty good shock," Mr Thomas, 59, said. "I looked at my boat outside. It was rocking. Everything was moving. My truck was moving." After the initial jolt, Mr Thomas began to check the hotel. "The fixtures and everything were still swinging," he said. "I had some picture frames coming down." Natural Resources Canada said in a statement that a major earthquake was felt across much of north and central British Columbia but that there were no immediate reports of damage. PrayForCanada became a worldwide trending topic on Twitter. "I was sitting at my desk on my computer and everything just started to move. It was maybe 20 seconds," said Joan Girbav, manager of Pacific Inn in Prince Rupert, British Columbia. "It's very scary. I've lived here all my life and I've never felt that."The quake was felt on the mainlaind in Prince Rupert, British Columbia, which is across the Hecate Strait from the islands. "Everyone felt it here," said city recreation director Rudy Kelly, who was setting up an evacuation center for people from the city's low-lying areas. He said the work was in anticipation of a tsunami wave. Prince Rupert resident Grainne Barthe said fire trucks had blocked access to the waterfront when she came out of a restaurant. "Everything was moving. It was crazy," she said. "I've felt earthquakes before but this was the biggest. It was nerve wracking. I thought we should be going under a table."