NAOOCalifornia has been issued with tsunami warnings
The monster quake hit 157 miles (256km) southeast of Chiniak, Alaska, at a depth of 10 km at 9.31am GMT, the US Geological Survey (USGS) said.
The earthquake in the Gulf of Alaska was about 400 miles (578km) south of Anchorage, which is Alaska's most populous city with a population of nearly 300,000.
Anchorage residents have been urged to move away from the coast amid warnings of an "extraordinary threat to life or property".
A tsunami watch is in effect for Washington State, Oregon, California, Hawaii and parts of Mexico, according to the Tsunami Warning Centre.Related articles
In California, tsumani warnings were put in place from the coast from the Californian/Mexico border to the Oregon/Californian border including San Francisco Bay.