A magnitude 8.0 earthquake has struck deep under the ocean
floor near Alaska's Aleutian Islands, triggering shaking that
could be felt for vast distances and prompting a tsunami
warning, the US Geological Survey and National Tsunami
Warning Center said.
The tsunami warning, later downgraded to an advisory,
prompted the evacuation of about 150 residents of the town of
Adak to higher ground, according to media reports. It was not
immediately clear whether the quake caused injuries or
The quake was so large and deep that it triggered dozens of
aftershocks within an hour and prompted enough shaking that
it will be picked up by seismometers around the world over
the next 24 hours, said Mike West, a seismologist who serves
as director of the Alaska Earthquake Center.
"When you've got an earthquake that big, it rings the Earth
like a bell," West said.
The warning covered coastal areas of Alaska from Nikolski to
Attu, officials said, adding that the level of tsunami danger
was being evaluated for other US and Canadian Pacific coastal
The US National Oceanic and Atmospheric Administration
initially warned of widespread, dangerous coastal flooding
and powerful currents in the region for hours in the event of
a tsunami. The warning was downgraded about two hours after
the earthquake hit.
A tsunami advisory, less severe than a warning, was in effect
for coastal areas of Alaska from Unimak Pass to Nikolski.
The quake struck shortly before 1pm (local time), about 23km
southeast of Little Sitkin Island, Alaska, at a depth of
about 114km, the USGS said.
Tsunamis are waves resulting from undersea quakes that can
measure several yards (meters) high and can overwhelm coastal
areas near and far, NOAA said. It takes a large quake of
magnitude 7.0 or higher to produce a tsunami, the center
In 2004, a tsunami produced by a magnitude 9.3 undersea
earthquake struck near Indonesia and 240,000 people were
killed, the center noted.