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Alaska Beat

Aftershocks of Monday's quake rumble across Southcentral Alaska

  • Author: Craig Medred
  • Updated: September 27, 2016
  • Published December 4, 2012

Aftershocks of a 5.8 magnitude earthquake that rattled Southcentral on Monday afternoon were still rumbling in Cook Inlet Tuesday morning.

As of 9:30 a.m. Tuesday, 27 aftershocks had been recorded by the Alaska Earthquake Information Center.

The most recent quake was at 8:37 a.m., 31 miles West of Anchorage.

The quakes vary in size, generally hovering around a magnitude of 2, however the largest aftershock to occur thus far was at a magnitude of 3.31, at 5:35 a.m.

The smallest recorded was at a magnitude 1.53, at 4:42 a.m. Tuesday.

Some of the quakes have not yet had their size analyzed by seismologists, and are marked simply with a magnitude "unknown."

Aftershocks are smaller earthquakes that follow a large one, originating from the same area as the bigger quake. For Monday's 5.8 rumbler, quakes within five to 10 miles qualify.

Jim Dixon, a seismologist with the Alaska Volcano Observatory, said that after a large earthquake rips the crust, it "may not have finished moving," and aftershocks are the earth continuing to shift.

The main quake is generally much larger than the aftershocks. Sometimes, large earthquakes are preceded by smaller ones, and those initial rumblings are called foreshocks.

The frequency of aftershocks and their magnitude should decrease with time, Dixon said.

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