A major earthquake of 7.4 magnitude hit in the Pacific Ocean Thursday 172 kilometres east of Atka, Alaska in the Aleutian Islands, at a depth of about 40 kilometres, and a tsunami warning was in effect for coastal Alaska, warning agencies said.
A second quake of the same magnitude hit in the same vicinity and at the same depth a half-minute later, the U.S. Geological Survey said.
"A Tsunami warning is now in effect which includes the coastal areas of Alaska from Unimak Pass, Alaska (129 kilometres northeast of Dutch Harbor) to Amchitka Pass, Alaska (200 kilometres west of Adak),'' the West Coast and Alaska Tsunami Warning Center said.
The center monitors tsunami risk only for the west coast of North America from the Mexican border to Alaska.
A tsunami warning means all coastal residents in the warning area who are near the beach or in low-lying regions should move immediately to higher ground and away from harbors and inlets, including those sheltered directly from the sea.
Earthquakes of this size magnitude are known to generate tsunamis. If a tsunami has been generated, the waves will first reach Adak, Alaska, at 8:12 p.m.