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Earthquake swarm not indicative of ... anything

Alaska Earthquake Center

  A spate of earthquakes widely felt in Southcentral Alaska lately has some wondering if that's a good sign or a bad sign, insofar as larger quakes are concerned.

Checking with Natalia Ruppert, a seismologist with the Alaska Earthquake Center in Fairbanks, reveals you can't make assumptions on future quakes based on what we're feeling now.

 "The scaling relationship between earthquakes of different magnitudes is not linear. Two magnitude one earthquakes do not equal one magnitude two earthquake. Its relationship is more complicated," she said. "So to have a enough small earthquakes to compensate for a magnitude seven, it would take thousands and thousands of those small earthquakes."

 So even though there is more than one earthquake reported every 15 minutes in Alaska, the small quakes cannot be seen as relieving pressure on the Aleutian mega-thrust fault and preventing a larger, say magnitude 7 or greater, earthquake from someday occurring. The Aleutian mega-thrust fault stretches from Prince William Sound to the Kamchatka Peninsula and dominates the tectonic geology of the region.

Conversely, Ruppert says earthquake science isn't precise enough to be able to tell if a moderate earthquake is a warning sign for an imminent big one.

 "When we have a magnitude 4 or magnitude 5 moderate earthquake that's felt, it's really hard to tell for us if it's going to lead up to a larger event, because seismology is still not at the point where we can accurately predict earthquake occurrence in the future," she said. "So the magnitude 5.3 that happened in Prince William Sound, we cannot tell if it's going to lead up to a larger event, or if it's just a normal earthquake that'll release a couple of aftershocks and will get back to normal."

 As far as the number of earthquakes that are happening, Ruppert says they have stayed roughly steady.

 "We did not notice any unusual changes in Alaska. It's still normal background earthquake level with large or moderate earthquakes once in a while. On average we might expect magnitude 7 or greater earthquake somewhere in Alaska per year," she said. "This is based on long term earthquake rates reported in Alaska."

 With an average of over one earthquake somewhere on the Kenai Peninsula per week, Ruppert says residents should take heed.

 "So that's just a reminder to them to be aware of the earthquake hazards in the region," she said. And it's not a bad idea to learn more about earthquakes and to know what to do in case of an earthquake emergency."

 The Alaska Earthquake Center has tips to help prepare for an earthquake and to mitigate the risk in your home and office.

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