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Earthquake lights in Peru?

  1. Aug 20, 2007 #1

    Ivan Seeking

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    I have to just throw this one out and see what comes. I have no idea if this is credible, but there are claims that local news agencies in Peru are reporting that earthquake lights were seen before and after the recent quake. There are a couple of videos included in the report.
    http://forgetomori.com/2007/science/earthlights-on-perus-earthquake/

    I am not familiar with this source.

    More on earthquake lights.
    https://www.physicsforums.com/showthread.php?p=416970#post416970
     
    Last edited: Aug 20, 2007
  2. jcsd
  3. Aug 20, 2007 #2
    From the latter link:

    "One of the more logical explanations of the cause of earthquake lights is the piezoelectric effect. Certain materials, including quartz, respond to changes in pressure by changes in electrical voltage across their surfaces. The idea is that, as quartz-bearing rocks are stressed, they might produce such high voltages that lightning-like discharges could occur in the air above.

    Earthquake lights have been described as looking like auroral streamers diverging from a point on the horizon. Beams like those from a searchlight have been reported. Other reports describe sheets or circular glowing regions, either touching the ground or in detached clouds above ground.

    The lights seem to show up best during the time of the main shock of an earthquake and also before and after. From a practical viewpoint, the lights before an earthquake seem most interesting since they shed light on the occurrence of the next large earthquake."
    .........
    The actual descriptions in the middle paragraph don't sound like sudden, lightning-like discharges predicted in the first, though.

    I believe the electric field created when a piezoelectric material is stressed is constant so long as the material remains stressed. This would explain why any lights due to such a field are seen both before and after a quake, and not just during the event.

    So, instead of a straightforward high voltage discharge, I'm wondering how plausible it would be to ascribe the lights to something along the lines of Thomson Scattering or Compton Scattering? I think I get the principle behind this kind of scattering, but a little bit of googling has failed to uncover whether the resulting wavelengths of light are ever in the range of visible light or not. If so, I think this tree would be better to bark up than the tree of high voltage discharge (and, sure, you can quote me on that): it better explains the more sustained phenomena reported. (Of possible importance: light scattered in this way is polarized.)
     
  4. Aug 20, 2007 #3

    berkeman

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    Too bad that any piezo lights or whatever would have to be confined to the event itself. The physics are probably real, and the visuals were probably interesting.

    Speaking as someone who lives on top of a major fault who is scheduled for 7.0 or bigger in the next few years, an hour of prior notice would be a huge help in our emergency response. Imagine being able to set up your EOC and pre-position your Fire Engines and call in all of your off-duty firefighters with 60 minutes notice! Plus being able to get people to evacuate dangerous structures and liquifaction zones. That's what we need -- something like a Tsunami warning for earthquakes....
     
    Last edited: Aug 20, 2007
  5. Aug 20, 2007 #4

    russ_watters

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    Right - zoob, piezo effect produces a voltage while there is a stress, but it only sticks around if there is no discharge. And it would be the discharge that produces the lightning-like effect.

    I'm not sure how long it takes for the shock wave of the earthquake to propagate, but it is possible that the "before" event actually happens when the earth starts moving but before anyone starts to feel it. The earth has to be moving for a piezo discharge to occur.
     
  6. Aug 20, 2007 #5
    Right, but there is no lightning-like effect. The lights are actually sustained phenomena, not mere flashes:

    "Earthquake lights have been described as looking like auroral streamers diverging from a point on the horizon. Beams like those from a searchlight have been reported. Other reports describe sheets or circular glowing regions, either touching the ground or in detached clouds above ground."
     
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