The warnings were lifted an hour or two after the quake, which struck at 2053 GMT some 15 miles (24 kilometres) southeast of remote Little Sitkin Island, in the western Aleutians.
No major damage was reported from the quake, which was initially registered at 8.0 and whose epicenter was about a depth of about 70 miles. It was followed by a series of aftershocks, including one 6.0 in magnitude.
"There was no panic," Layton Lockett, city manager in the town of Adak, told AFP after he sounded the alarms to evacuate the 150 or so villagers and Navy contractors to higher ground.
"We're a rough and tumble kind of group. We're used to certain types of earthquake, some are stronger.. this one was a little bit more," he added, saying that everyone was back down two hours after initial alert.
The National Tsunami Warning Center initially issued a warning for coastal areas from Nikolski on Umnak Island to Attu Island at the far western end of the Aleutians.
In those areas, "widespread dangerous coastal flooding accompanied by powerful currents are possible, and may continue for many hours after tsunami arrival."
It also said the level of tsunami danger for other US and Canadian Pacific coasts was being evaluated. But the warning triggered by the quake was later downgraded to an advisory.
Lockett said locals are used to earthquakes -- and official brief Navy contractors who arrive for stays working on the remote islands.
"If the earthquake lasts longer than 20 seconds or is significant, or if they fall over, they're to go up on the hill," he said.
On this occasion "it actually went off pretty well. We're thankful that nothing happened, and now we're at the inspection stage," he said, adding that there was "no obvious damage."
"We would expect that the buildings would be fine. We're more worried about the main infrastructure such as roads, if they've cracked at all, water and sewers, electrical.
"So we'll be inspecting those ... but I think we're fine."
Monday's quake is the strongest in the region since 1965, when an 8.7 magnitude quake shook nearby Rat Island, according to USGS figures cited by local media.