A dozen measurable aftershocks have already hit the region since Friday's quake, including one reaching 6.1 in strength, said seismologist Michael West. There have been more than 30 aftershocks measuring at least magnitude 2.5.
None of the aftershocks are expected to cause a notable tsunami, since the initial quake did not cause one. And West said experts are not too worried this quake will trigger another significant quake nearby in the near future.
"This is very common area for earthquakes," West said. Temblors above magnitude 5.0 are felt every month.
The site of Friday's quake is quite active. Significant quakes were felt just to the east and the west of Friday's earthquake in 1986, 1996 and 2003.
"This was exactly the earthquake that's supposed to happen," West said, noting that it's part of a pattern, when examined in a scientific way.
The Pacific tectonic plate is always pushing under America. It builds up stress and then earthquakes happen. Of course, West notes, he has be cautious about saying something will never happen, but he's not particularly concerned.
There have been no reports of damage or injuries from the earthquake, which was strongly felt in Atka, an Aleut community of 64 people, and the larger Aleutian town of Adak, where 320 people live.
The earthquake and the aftershocks didn't trigger any tsunami warnings, but Michael Burgy with the West Coast and Alaska Tsunami Warning Center in Palmer, Alaska, said the center is monitoring for potential tsunamis caused by landslides, either on land or under water.
The Alaska Earthquake Information Center said the primary earthquake was centered 67 miles southwest of Adak, about 1,200 miles southwest of Anchorage. Shaking lasted up to one minute.
The 6.1 aftershock struck in the same general area at 10:39 p.m. Friday.
The 7.0 quake occurred offshore in the subduction zone where plates of the Earth's crust grind and dive. By contrast, California's most famous fault line, the San Andreas, is a strike-slip fault. Quakes along strike-slip faults tend to move horizontally.
The communities are located in a sparsely populated region and both played roles in World War II.
Atka residents were displaced during the war, relocating to Southeast Alaska so the U.S. government could demolish the village to prevent the Japanese from seizing it as they had other Aleutian communities. After the war, the U.S. Navy rebuilt the community and residents returned. Today, the community is a cluster of solidly built utilitarian buildings scattered over rolling hills that turned emerald green in warmer months.
Adak, 110 miles to the west, had been home to U.S. military installations that allowed forces to wage a successful offense against the Japanese after they seized the Aleutian Islands of Kiska and Attu. After the war. Adak was transformed into a Naval air station that served as a submarine surveillance center during the Cold War. Later, the facilities were acquired by the Aleut Corp. -- a regional native corporation -- in a federal land-transfer agreement. It became a city in 2001 and today retains its military appearance.
Associated Press writers Donna Gordon Blankinship in Seattle and Alicia Chang in Los Angeles contributed to this report.
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