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Powerful Aftershocks Strike Following 7.9 Magnitude Alaska Earthquake

(CBS SF) - A massive 7.9 magnitude earthquake Monday in the Aleutian Islands was quickly followed by smaller 5.9 and 6.0 quakes closer to land.

The original quake set off a Tsunami warning after striking deep in the water east of Little Sitkin Island. That was quickly followed by a handful of smaller quakes closer to land. Those tremors ranged in size from magnitude 3.7 to 6.0. All were centered at least 100 kilometers beneath the Earth's surface.

A magnitude 6.9 earthquake struck the area around 6 p.m. Pacific Time.

Seismographs originally measured the initial quake as a 7.1 but the U.S. Geological Survey quickly upgraded that number to an 7.9. That's a departure from the usual pattern where quakes are more often downgraded.

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Another massive quake registering 6.9 struck just before the Alaska quake, this one on the polar opposite side of the ocean, north of New Zealand.

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