There were no initial reports of casualties or damage.
The quake, which hit at 0310 GMT, was at a depth of 11.4k m (7.1 miles) and 94 km (58 miles) south of Port Hardy, Canada.
The US agency had initially reported a magnitude of 6.7.
The US tsunami warning office in Palmer, Alaska said there was no tsunami danger for potentially affected areas: Alaska, British Columbia, Washington, Oregon and California.
Port Hardy Mayor Bev Parnham said no one in the town was injured but she said "pretty much everyone felt it -- it was quite a shake."
"Our infrastructure is in place and there's no damage that we've been able to see," she said, according to The Vancouver Sun.
AFP