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"Slow" Earthquakes May Help Predict Major Quakes

Posted by Hemos on from the rocking-and-rolling dept.

Iphtashu Fitz writes "Think all earthquakes last only seconds or minutes? Think again! Scientists at the University of Washington are measuring a "slow" earthquake some 12 to 25 miles underground that could last as long as a month. Along with the UW scientists, seismologists at the Geological Survey of Canada and Central Washington University have documented at least nine previous so-called slow earthquakes going back to 1992. They seem to occur every 14 months or so, the last one occuring in February and March of last year. These earthquakes, also known as slow-slip earthqakes, can release as much energy as a magnitude 6.8 earthquake but because it's released over such a long period of time nobody on the surface even notices it. One key question the scientists are trying to answer is whether these slow earthquakes add to or relieve stress in the tectonic plates, which could ultimately help to predict major earthqakes."

5 of 107 comments (clear)

  1. I think it's scary... by Mz6 · · Score: 5, Insightful
    Considering that the largest earthquake ever in Washington was a 7.3 in 1874 and that this was largely just discovered a few years ago, perhaps this is a precursor to something big about to happen? More recently was a 1949 earthquake that measured 7.1 near Olympia.

    From the Science Daily article..."Making that determination will help in understanding whether they are adding to or relieving stress in the Cascadia subduction zone off the Washington and B.C. coast, where the Juan de Fuca plate dives beneath the North American plate. The subduction zone is capable of generating great earthquakes, and scientists recently determined that a Cascadia earthquake in 1700 measured about 9.0 in magnitude."

    And Wired... "The coastal region of northwest Washington state and southeast British Columbia is prone to earthquakes, and scientist warn the area gets hit with a devastating shake of magnitude 9 about every 500 years."

    Sure.. we're only 196 years off the 500 year mark since the last 9.0, but for it only to pop up a few years ago makes it seem very ominous.

    This data, while very interesting, could still go 2 ways. It is helping to alleviate and prevent major earthquakes in that area, or it's a major precurosr to a huge event that could happen in the near future. The hard part? What is considered teh near future... tomorrow? 5 years? 10 years? Guess we'll have to wait and see.

    What's even more interesting is that I have yet to see any reports about this coming from any of the California plates, perhaps it hasn't been found or tested for or it's just not there.. Who knows.

    --
    Hmmm.
    1. Re:I think it's scary... by Blakey+Rat · · Score: 3, Insightful

      What's really scary is that the local government isn't doing crap about making the city more earthquake safe.

      Look at the Alaskan Way Viaduct, for example. An almost identical freeway in California collapsed in the 1989 earthquake. There's been a lot of lip-service about making the viaduct safe, but the only changes I've seen is the installation of a few metal braces on a couple of the supports. That's not good enough!

      That viaduct needs to be torn down. If there's any weak point in Seattle's earthquake strategy, that's it.

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      Comment of the year
    2. Re:I think it's scary... by WhiteBandit · · Score: 4, Insightful

      Also note the 500 year mark is fairly arbitrary in that it is an average.

      Down here in Southern California, we've looked at a spot where the San Andreas fault crosses through the Cajon Pass. Digging trenches and things across the fault reveals movement on average every 180 years or so.

      The last time that segment of the fault moved was in 1812. 192 years and counting. When you actually plot out when earthquakes occured, you find major events happening as close to 60 years apart to as far away as 220.

      So basically, you guys might be due for an earthquake fairly soon... or you might not! ;)

  2. I'm still waiting.... by TastyWords · · Score: 4, Insightful

    ...to hear whether piezoelectricity can be used to detect quakes as well. With all of the smashing and crashing going on, one would think it would have the potential to generate radio waves such that a properly tuned instrument could receive|detect the signal.

  3. add to or relieve stress by ron_ivi · · Score: 4, Insightful
    "One key question the scientists are trying to answer is whether these slow earthquakes add to or relieve stress in the tectonic plates, which could ultimately help to predict major earthqakes."

    Wouldn't it do both. I.e. relieve stress in the spot that slipped, and add to stress in the spots where the plates are still binding?