The quake hit 256 km (157 miles) southeast of Chiniak, Alaska at a depth of 10 km at 0931 GMT, the U.S. Geological Survey said.
“If you are located in this coastal area, move inland to higher ground. Tsunami warnings mean that a tsunami with significant inundation is possible or is already occurring,” Anchorage Office of Emergency Management said in a warning for Alaska and British Columbia.
Tsunami warnings for parts of Alaska and Canada and a tsunami watch for the entire U.S. west coast and Hawaii were issued.
“Based on all available data a tsunami may have been generated by this earthquake that could be destructive on coastal areas even far from the epicentre,” the Pacific Tsunami Warning Center said.
Japan’s meteorological agency said it was monitoring the situation but did not issue a tsunami alert.