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Space Science

Earthquakes Detectable From Space by GPS 25

Posted by timothy from the eye-in-sky dept.
Iphtashu Fitz writes "Research sponsored mainly by the European Space Agency has demonstrated that earthquakes generate acoustic signals, almost like a huge loudspeaker, that can be detected from space. According to an ABC News Science/Technology article, geophysicist Juliette Artru came up with the concept while working on her doctorate degree. By monitoring an array of GPS receivers located throughout California she was able to determine that a massive 7.9 earthquake in Alaska last year resulted in the constillation of GPS satellites generating a mesaurable amount of interference. According to Artru, "A displacement of one millimeter on the ground can cause a displacement of 100 meters in the ionosphere," so a tiny pressure wave created by an earthquake can undergo huge amplification by the time it reaches the ionosphere. The resulting shockwave causes a tiny but very distinct pattern of interference in the GPS signals broadcast by the satellites."
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Earthquakes Detectable From Space by GPS More

Earthquakes Detectable From Space by GPS

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  • This is great! (Score:3, Funny)

    by phraktyl ( 92649 ) * <wyatt@drag g o o.com> on Wednesday November 12, 2003 @12:15PM (#7454257) Homepage Journal
    I for one have had a hard time in the past detecting the ground shaking under me here on the surface of the earth, what with the dishes rattling off the shelves and pictures falling off the walls and all. Now there is a way to know for certain!
    • Not only that, but now we can know with 10-meter accuracy where the epicenter is!

      No more wondering if this is really the worst of it! No more guessing who's getting rocked the hardest! No more letting your neighbor claim bragging rights to hosting the epicenter in his pool when clearly the center is in YOUR yard, give or take a few feet!

      GTRacer
      - Unless we're at war, and then you're stuck with 100M accuracy ;)

  • "A displacement of one millimeter on the ground can cause a displacement of 100 meters in the ionosphere,"

    So presumably the same technique can be used to detect stealthed underground nuclear bomb tests as well.

    Next question: do arrays of GPS devices exist in India, Pkistan, and China? If not, could they be put in place easily and stealthily, as by airdrops of a number of small GPS receivers designed to transmit results to another sattelite?
    • Underground nuke test can already be detected. They use a new device called a seismograph.

      That is one of the ways the US/USSR/China monitored each others tests
      • Underground nuke test can already be detected. They use a new device called a seismograph.

        Not always. Pakistan's nuclear tests were right on the edge of what the US network can detect; in fact, some of the tests were not noticed until after Pakistan announced that they had occurred, and researchers went back through the records.

        In general, seismographs can detect a nuclear explosion of half a kiloton yield or larger.
    • Actually I don't think the location of the GPS receivers is all that important, other than the fact that they're located somewhere other than the event that occurs. I would guess that they need to remain stationary in order to detect the fact that the signals from the GPS satellites have fluctuated. I suppose you might need a group of receivers somewhere in the eastern hemisphere so that they're receiving signals from the satellites that are over the geographic area you're interested in (the ones most lik
    • I believe the military already has an air deployable acoustic monitor with built-in GPS locator called the ADAS.
      • Interesting. I just found references to the acronym ADAS: "Airborne Data Automation System". Don't know if this is what you're referring to but it sounds like it could be. Google doesn't show much other than some links to the acronym & definition on some military websites.
    • I did not think the original post made clear whether interference means small positioning errors or difficulty getting any readings from some of the GPS receivers. Also is an array 3 receivers or 300 or something in-between? If the data is from a satellite that is changing altitude one meter per second, due to shock waves from the earthquake we should expect plus or minus one meter errors due to dopler shift of the satellite signal, if for no other reason. I presume data is typically from a GPS satellite
  • we don't care about an earthquake unless it's big enough to disrupt my car's Nav system while stuck in traffic on the 405.

  • Further info: (Score:3, Informative)

    by Saint Aardvark ( 159009 ) * on Wednesday November 12, 2003 @03:13PM (#7456295) Homepage Journal
    Juliette Artru's homepage [caltech.edu] has further information on her research [caltech.edu]. Particularly interesting is the application of this technique to tsunamis: "This observation opens exciting perspectives for the study of tsunamis, not only for early warning purposes but also to characterize their propagation in the ocean."

    A paper [caltech.edu] of hers from 2001 presents information on the Mount Pinatubo eruption. An abstract of the paper discussed in the ABC story is also available [agu.org].

  • Do it with bistatic shortwave? (Score:4, Interesting)

    by G4from128k ( 686170 ) on Wednesday November 12, 2003 @04:07PM (#7457067)
    If small ground motions propagate to large amplitude acoustic effects in the ionosphere, then the effects should be detectable with shortwave radio. A bistatic transmitter-receiver pair would be configured to bounce its signal off some part of the ionosphere. Acoustic vibrations in that layer should create detectable distortion in the shortwave signals. It may not be as exciting as GPS, but it may enable detection of ionospheric disturbances over inaccessible parts of the planet by locating the bistatic pair on either side of the region.

  • eek... (Score:3, Informative)

    by M-G ( 44998 ) on Wednesday November 12, 2003 @06:39PM (#7459049)
    from the article: ...the displacement sends out an acoustic signal, or radio wave, that moves up through the atmosphere.

    Uh, is it an acoustic wave, or a radio wave? There is a difference.

    From the post: resulted in the constillation of GPS satellites generating a mesaurable amount of interference.

    The constellation of GPS satellites did not generate any interference. Rather the effect of the wave on the ionosphere caused interference in the RF signals from the GPS sats.

    • yeah the acumacy of wordage only in an article not in his post very good isnt.

      it's quite hard to read sometimes, and as you've pointed out, often blatently wrong. i have not RTFA, but that quote makes me inclined not to bother :/
  • By monitoring an array of GPS receivers located throughout California she was able to determine that a massive 7.9 earthquake in Alaska last year resulted in the constillation of GPS satellites generating a mesaurable amount of interference.

    Unless this is a new technique, GPS has been used for years by geologists looking for earthquakes and crust movement(and I don't mean the lojack in grandma's blueberry pie).

  • Firstly, I think some of the "acoustic" vs "radio" waves confusion will have been caused by a cross reference to the ELF schumann resonances - a far more (IMO) useful quake research technique.

    This discovery (the only really interesting bit is a way to detect the perturbations using existing equipment) is well and good for post-event quake analysis, but is of limited use for prediction and harm minimisation.

    It is well known that ELF waves are detected in a crescendo that peaks (and dissapears) 48 to 72 h

  • Comment removed based on user account deletion

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