Earthquakes and the Moon

Discussion in 'Science' started by Matt_NZ, Jan 20, 2011.

  1. Matt_NZ

    Matt_NZ Member

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    This seems to be controversal subject after looking it up a bit. A few people say that yes, the moon does influence the quakes while a group of scientists say that no, it's not possible.

    I have to say, I'm tending to agree with the group that think that the moon does have an influence. Everytime we have a swarm of earthquakes here in Chirstchurch, it always within a few days of a full moon. Infact, based on the previous months swarm, I had already assumed that today would be the day the next swarm hit and that turned out to be true with a nice big 5.1 shallow shake early this morning and a series of shallow aftershocks following.

    The usual argument given back as to why it can't be true is that the moon is too small to have an influence...however it has an effect on the tides and weather, so why wouldn't it create a pull on the ground as well?
     
  2. daztay

    daztay Member

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    Since no one has replied I'll give it a bump.

    I dont think the moon could effect solids. But I wonder if it can effect the water beneath the earth (under ground streams).
    Tidal effects can make the water table rise inland from the ocean.
    Whether this could effect the plates deep below, I dont know.
     
  3. Foliage

    Foliage Member

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    Because the ground is gigantic and the ocean is tiny in comparison? Because the ground is solid and the ocean is a liquid?

    Regarding the full moon that just sounds like confirmation bias to me. Get a list of every single quake in the last 2 years and work out what percentage of them fell on a full moon, I'll bet you will find there is no correlation, if there was someone would have studied it by now.
     
  4. itsmydamnation

    itsmydamnation Member

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    i cant agree with you logic, look at this:
    http://rses.anu.edu.au/~malcolm/papers/pdf/Sambridge-etal-2010.pdf
    only published this year, almost as simple of an analysis as you can get based off an idea thats well known and over 100 years old, yet someone hadn't studied it until now.
     
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    Matt_NZ

    Matt_NZ Member

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    I don't think the moon will be responsible for every earthquake but I don't see why it couldn't have some involvement where the earth might be weak or under strain where the slightest pull might be enough to trigger the plates to snap.

    It just seems quite coincidental that Christchurch gets a swarm of earthquakes around the period of a full moon and then things go somewhat quiet again before the next cycle. I suppose it could just be that the two are cycling together, if earthquakes work in cycles.
     
  6. oculi

    oculi Member

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    wow the collective for earthquakes is swarm, i thought it would be "rumble" or something.

    Are you saying that the gravitational effect of the moon is somehow dependant on how much of it is lit by the sun? unless i'm missing something the moon is still there even if you can't see it.

    i'm sure the moon has some influence on earthquakes, but i'm just as sure the internal mechanics of the earth has a larger influence.
     
  7. mshagg

    mshagg Politburo

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    Im not sure this observation stands up to a suitable level of confidence, it doesnt really demonstrate that one is influencing the other?
     
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    Matt_NZ

    Matt_NZ Member

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    Yeah, but the full moon indicates the position of the moon in relation to the earth and sun - in the case of the full moon the sun is on one side of the earth and the moon on the other. I really don't know if it means anything at all - I guess I, like others here in Christchurch, are just trying to find a way to understand this whole earthquake stuff :|

    I don't actually know what a collective of earthquakes would be called but a swarm sounded appropriate lol.
     
  9. aXis

    aXis Member

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    Intuatively you'd assume that all that mass of ocean moving around with the tides would create some stresses on the crust, but when you think about it properly the gravitational forces should be balanced anyway.

    That said I wouldnt not be suprised if it had an effect, even a fraction of a percent could be enough to trigger quakes that are on a threshold.
     
  10. Foliage

    Foliage Member

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    Well if you aren't willing to actually get some data and do some maths then I don't really know what the point of this is, saying "I think this is the case" because you've had a few tremors on full moons isn't going to hold up in the science forum.
     
  11. Jesmol

    Jesmol Member

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    Can I make the blatantly obvious point that the moon does not change in mass when it becomes full. Therefore the gravitation influence of the moon doesn't change because of its phase.
     
  12. DavidRa

    DavidRa Member

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    I believe you missed the point.

    However, I think you'd find concentrations around the new moon as well as the full moon. From my understanding:

    Full Moon
    Moon ---- Earth --------------------------------------------------------------- Sun

    New Moon
    Earth ---- Moon --------------------------------------------------------------- Sun

    In both cases there is slightly more effect from gravity - once because the bodies are pulling in opposite directions and once in the same direction.

    At say a half moon, the moon is pulling sideways on the earth (80-100 degree angle from the Sun) and thus the effective force is changed.

    Bah, I'm not explaining it that well. I think the hypothesis has merit, but it needs evidence.
     
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    Matt_NZ

    Matt_NZ Member

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    Isn't the moon also what keeps Earth on a tilt? If it can keep it on a tilt, couldn't it also create some kind of pull on the crust as well?
     
  14. jkmatt

    jkmatt Member

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    Would/does it have an effect on the magma? Like a slight "magma tide"? No idea how that could or would be measured.
     
  15. SaTaN

    SaTaN Member

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    the moon doesnt control the tilt, and it bloody doesnt make the tides either! Why is all the water staying on earth if the moon has so much pull? for that matter, why isnt it all flying off to the sun or jupiter which has far more gravitational pull? "Because earths gravitation pull is keeping it there" you say? well thats crap. Gravity is the weakest of all forces, it falls off at inverse square distance which means at sea level the gravitational force of earth is infinitely greater than that from the moon so the water cant be pulled off. Care to explain why earth has an atmosphere which isnt pulled away by the moon but the water is?
     
    Last edited by a moderator: Mar 19, 2011
  16. Foliage

    Foliage Member

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    Actually it does lol, and on some of jupiters moons it actually does cause cracks in the crust.
     
  17. vladesch

    vladesch Member

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    The extreme vulcanism on Io is attributed to the extreme tidal forces it is subjected to, so I don't see why not. Probably not much of an effect though because our moon is extremely distant in comparison.
     
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    Matt_NZ

    Matt_NZ Member

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    Probably the wrong time to talk about it, but again, another batch of big earthquakes around a full moon cycle in Christchurch :(
     
  19. turiya

    turiya Member

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    Correlation != causation

    There may be a very minimal effect from the moon, but given that you're talking about the moon affecting bedrock multiple kilometres below earths surface I suspect it is highly unlikely that the moon will contribute anything noticeable. It certainly won't cause earthquakes. And what are you going to do if it could be proven that it did? Tow it away? Evacuate cities once every month? All the evidence pointing to this theory is anecdotal and co-incidental.
     
  20. ikonz0r

    ikonz0r Member

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    *yawn*

    ok.


    Of course its possible. It's called Tides. If there was no moon the earth would actually be rotating a lot faster. This has been proven. Like wise with any 2 gravitationally bound objects they both have an effect on each other. The most tectonically active body in the solar system is Io, one of Jupiters moons and it is so due to the tidal forces that Jupiter plays on it. Over 400 active volcano's spewing lava.

    This may be true however un-likely

    Full moon occurs when the moon is furthest from the sun, so you won't have a double gravitational effect form moon and sun. A new moon (Dark) however could increase the pull.

    Next factor is weather or not the moon is in Apogee or Perigee. (keep in mind the difference in distance is some mere 5%.. as mentioned somewhere above due to gravity being an inverse square law i doubt this will have much of an effect)

    Another factor is if the earth is at perihelion or not.

    Another factor to consider is the time of day (Is christ church closest to the sun / moon combination)

    Oh it does, Infact the ground moves something like 1ft in altatude due to the tides. Water moves a lot more as it's much lighter.


    Anyway, to sum it all up. It is possible there was a freaky co-incidents of all those factors aligning to make a major gravitational change.. but I think you'll find its just unfortunate timing as the tectonic plates are just doing what they're doing, and the moon happened to be out :thumbup:
     

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