The U.S. Geological Survey (USGS) said the quake occurred at about 1:30 a.m. Alaska time (1030 GMT), and was centered nearly 260 km southwest of Anchorage.
The offshore epicenter was about 80 km deep.
The Pacific Tsunami Warning Center in Hawaii said a tsunami was not expected “because the earthquake is located too deep inside the earth.”
However, some residents of Anchorage, the biggest city in the northernmost U.S. state, were awakened as their homes were shaken for 30 to 45 seconds.
According to reports reaching here, while there were power outages at some communities, authorities there have so far received no reports of casualties or major property damage.