The very strong quake was located about 56 miles (91 kilometers) east southeast of Perryville, Alaska, and occurred around 10:15 p.m. Wednesday night local time, USGS said.
At 29 miles deep (46.7 km), the earthquake is considered shallow. Shallow earthquakes are between 0 and 70 km in depth.
There have been at least two strong aftershocks, including a preliminary magnitude 6.2 and magnitude 5.6, the USGS reports.
A tsunami warning has been issued for portions the the state, according to the U.S. National Tsunami Warning Center.
They include South Alaska and the Alaska Peninsula, from Hinchinbrook Entrance, (90 miles east of Seward) to Unimak Pass, and for the Aleutian Islands, from Unimak Pass (80 miles northeast of Unalaska), to Samalga Pass, Alaska, which is 30 miles southwest of Nikolski.
A tsunami watch has been issued for Hawaii, according to the National Weather Service Pacific Tsunami Warning Center.
The level of tsunami danger is being evaluated for other US and Canadian Pacific coasts in North America, according to the NWS.
This is a developing story and will be updated.