Aftershocks from Friday's quake likely on Alaskan island

But not expected to cause a significant tsunami

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ANCHORAGE, Alaska -- Dozens of noticeable aftershocks above magnitude 4.0 are expected in the remote Aleutian Island region off Alaska in the days and weeks following a major 7.0 earthquake, the Alaska state seismologist said Saturday.

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.