The US Tsunami Warning System put millions on tsunami watch.
- A 7.9-magnitude quake hit off coastal Alaska early on Tuesday.
- It prompted authorities to issue widespread tsunami warnings.
- An area from Alaska to the edge of Mexico was initially covered.
- However, these warnings were later rolled back to just Alaska.
- Locals in Kodiak, an island off the coast of Alaska, were woken by sirens and warned to seek high ground.
Thousands of Alaskans evacuated their homes after a powerful earthquake struck off the coast of the state, generating a small tsunami.
People on Kodiak Island, off the coast of Alaska, were woken in the small hours of the morning by warning sirens and police officers urging them to retreat to high ground further inland to avoid the worst effects of a surge.
The warnings followed a 7.9-magnitude quake, which struck 25km below the sea floor in the Gulf of Alaska, at 12.23 a.m. Alaska Standard Time (9.31 a.m. GMT).
Authorities initially thought a resultant tsunami could travel far further than Alaska, and put the entire western coast of the United States on "tsunami watch," but this warning was later cancelled.
Initial data recorded by Alaskan weather monitors said a tsunami did occur, but was very small: Less than 1ft in height. Earlier reports from deep-sea buoys in the Gulf of Alaska had suggested the waves could be as high as 10 meters.
The US Tsunami Warning System first alerted people in Alaska shortly before 1 a.m. local time, around half an hour after the quake struck.
According to the US Geological Survey, the earthquake hit 157 miles southeast of Chiniak, Alaska. Its magnitude, initially reported as 8.2, was later revised down to 7.9.
Eighteen more earthquakes, from magnitude 2.5 to 5.6, have been detected so far in the wake of the initial tremor.
Alaska and parts of Canada were given tsunami warnings, the highest level of alert. As of 3.30 a.m. Alaska time, the warnings had been downgraded around Kodiak to "tsunami advisory," which indicates a moderate risk.
"Tsunami watch," a lesser state of readiness which was active from Washington state down to California, and also in Hawaii, was called off.