An 8.2 magnitude earthquake struck off the Alaskan peninsula late Wednesday, the United States Geological Survey said, generating small waves but no major tsunami.
The earthquake hit 56 miles (91 kilometers) southeast of the town of Perryville, the USGS said.
The quake struck at 10:15 pm Wednesday (0615 GMT Thursday). Perryville is a small village about 500 miles from Anchorage, Alaska's biggest city.
The US government's National Tsunami Warning Center immediately issued a tsunami alert for south Alaska and the Alaskan peninsula.
It initially warned of hazardous waves over the next three hours.
But after nearly three hours the maximum height detected by the center was eight inches (21 centimeters) and it downgraded the tsunami threat alerts to advisories.
Tsunami warning sirens had been broadcast across Kodiak, an island with a population of about 6,000 people, along Alaska's coastline.
Small waves hit the coast of Kodiak, according to a broadcaster on local radio station KMXT. She said authorities had lifted evacuation orders, with no reports of any damage.
"This is the largest earthquake to happen in the Alaska region since 1965," Michael West, state seismologist with the Alaska Earthquake Center, told Alaska Public Media.
Alaska is part of the seismically active Pacific Ring of Fire.
Alaska was hit by a 9.2-magnitude earthquake in March 1964, the strongest ever recorded in North America.
It devastated Anchorage and unleashed a tsunami that slammed the Gulf of Alaska, the US west coast, and Hawaii.
More than 250 people were killed by the quake and the tsunami.
A 7.5 magnitude earthquake also caused tsunami waves in Alaska's southern coast in October, but no casualties were reported.