The Alaska earthquake struck around 160 miles off the coast of Chiniak at 9.31am GMT on Tuesday, January 23.
WPTV Network issued the warning and said: “The Associated Press reports an 8.2 magnitude earthquake hitting off the Gulf of Alaska. A ‘watch’ warning has been issued for California, Washington and Oregon.
“And the big concern at this point is the tsunami warning that’s been put in effect for much of California and that includes the San Francisco Bay area.
“There’s no information at this point as far as any damage that this earthquake may have caused.
“But it’s something we are going to be keeping an eye on as this morning continues on.”
Those in affected areas have been urged to seek high ground as a tsunami warning is issued for parts of the California coast, all Hawaiian islands, Canada and Alaska.
Reports on social media suggest the tremors were felt as far south as Seattle and Vancouver.
The United States Geological Survey (USGS) has since downgraded the quake to a magnitude of 7.9.
Alaska is located on the Ring of Fire, a huge area in the basin of the Pacific Ocean where earthquakes and volcanic eruptions frequently occur.
Details on damage and casualties have not yet emerged. But the US Tsunami Warning Centre said there appears to be no immediate threats but the issue is “still under investigation”.
Heather Rand, who was in Anchorage, said the earthquake “was a slow roller, so it was felt for at least a minute before the real rolling started. Nothing fell off the walls and I didn’t have to wake my kiddo.
“It was a very long, slow build up. Creepy, more than anything. Definitely the longest, and I was born here.”
The Pacific Tsunami Warning Center said. “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 epicenter.”
A tsunami watch is in effect for California, Oregon and Washington, according to the Tsunami Warning Center.