A major earthquake measuring a preliminary magnitude of 7.1 has rocked remote portions of Alaska, the U.S. Geological Survey reports. The USGS issued, then canceled, a tsunami warning for Alaska's Aleutian Islands. It also lowered the magnitude to 6.8.

Updated at 11:22 a.m. ET: Alaska Native News has weighed in on the quake, noting that the area "is frequented by earthquakes every day, although a majority of them have a magnitude less than this."

The website, which describes itself as "news for the people of the last frontier," says there have been numerous quakes in the region in the past week, with most of the big ones centered off Kodiak Island, far out to sea.

Updated at 10:51 a.m. ET: It's worth noting that a 6.4 magnitude earthquake later rocked northern Argentina, but the epicenter was almost 370 miles underground. Agence France-Presse reports that there were no immediate reports of casualties or damage.

A quake measuring 7.0 hit the same sparsely populated region in January. The epicenter of that quake was also very deep and the effect at the surface was limited.

Updated at 10:26 a.m. ET: Paul Whitmore, director of the West Coast and Alaska Tsunami Warning Center in Palmer, Alaska, says the community closest to the Alaska earthquake is Atka, a village of about 60 people about 100 miles west of the epicenter. The quake was centered about 1,000 miles from Anchorage.

Updated at 10:06 a.m. ET: An aftershock measuring 4.5 hit the area about a half hour after the initial quake, the U.S. Geological Survey says. The initial quake was about 22.1 miles deep, USGS says. Earlier reports had it much closer to the surface.

Updated at 9:25 a.m. ET: The Aleutian Islands are no stranger to earthquakes. Agence France-Presse reports that the islands sit on the Pacific Ring of Fire, a "horseshoe-shaped seismic belt 25,000 miles long where most of the world's earthquakes and volcanic eruptions occur."

Updated at 9:00 a.m ET: The USGS has lowered the magnitude of the quake to 6.8.

Updated at 8:50 a.m. ET: The tsunami warning was canceled after only a small wave was recorded near Atka, Alaska, the Associated Press reports. "In Atka, they had a little bump of a wave, but nothing of any kind of a destructive power. Just a wave," said Jeremy Zidek, a spokesman for the Alaska Department of Homeland Security.

Updated at 8:27 a.m. ET: The tsunami warning has been canceled.

Updated at 8:15 a.m. ET: AP reports that a woman who answered the phone at the city hall in Unalaska but declined to give her name said people at Dutch Harbor were awakened by sirens. "We have some people on high ground, but not a lot," she said. "Sirens woke us all up — everybody's moving."

Updated at 8:07 ET: CNN reports that the shallow depth of the quake -- 6.2 miles -- would make it capable of causing damage. It struck, however, in a sparsely populated part of the Aleutian Islands, the Geological Survey said.

Updated at 7:55 a.m. ET: National Oceanic and Atmospheric Administration is urging all coastal residents within the tsunami warning area to move inland to higher ground and away from all harbours and inlets, including those directly sheltered from the sea.

People who felt the earth shake may see unusual wave action or may see the water level rising or receding. If so, they may have only a few minutes before the arrival of a tsunami, NOAA warned.

Original post: The USGS says the earthquake struck in the waters southeast of Atka, Alaska, in the north-Pacific island chain at about 6:55 a.m. ET, and there are no initial reports of injuries or damage, Reuters reports.

The tsunami warning is in effect for coastal areas of Alaska from Unimak Pass to Amchitka Pass. The areas are very remote and not heavily populated, according to Jessica Sigala, geophysicist with the USGS in Golden, Colo.

The Pacific Tsunami Warning Center said it did not see a threat of a Pacific-wide destructive tsunami from the quake.