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Earthquake prediction

  1. Apr 21, 2012 #1
    The seismic waves of earthquake travels at around 5 km/s. Wouldn't it be possible to setup network of detectors through out the world, and pre-warn people about approaching earthquake in real-time?
     
  2. jcsd
  3. Apr 21, 2012 #2

    Evo

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    Are you suggesting that once an earthquake happens that it starts traveling to other areas?
     
  4. Apr 21, 2012 #3

    Bobbywhy

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    I had the misfortune to be asleep in my bed in Sherman Oaks (San Fernando Valley) of Los Angeles in January, 1994 during the "Northridge Earthquake". My building was totally trashed and I was uninjured, but in shock. (which is actually a "mental injury")

    According to our information I was about 10 km from the epicenter of the earthquake. That translates to around two seconds warning time according to your numbers. Two seconds notice would not have helped one bit. Now those located 50 km away (ten seconds) only felt some mild shaking and no damage whatsoever.

    There is a massive network of seismic sensors, especially along the San Andreas Fault.

    “Getting information from the sensors is easy. Tying that information into a system where Inland Empire (metropolitan Los Angeles) residents might have as much as a 30-second notice that seismic waves were approaching is a much harder task. Such systems are already in place in Japan, but USGS geophysicist Doug Given, who is overseeing this project, said a similar network here is years away.”

    http://www.pe.com/local-news/reports/inland-quakes/inland-quakes-headlines-index/20090608-new-earthquake-sensors-installed-along-inland-areas-san-andreas-fault-line.ece [Broken]
     
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  5. Apr 22, 2012 #4

    Evo

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    That's terrible, glad you are ok.

    Please remember to put information taken from other websites in quotes.

    I'll admit to being skeptical about the benefits of earthquake warning systems. Of course it's too soon to know how much actual benefit they can be to the general population. Unfortunately those closest to the epicenter are unlikely to get any warning.

    http://www.pcworld.com/businesscent...sensors_in_focus_after_new_zealand_quake.html
     
  6. Apr 22, 2012 #5
    Of course, people closest to the epicenter won't benefit, but lets think about who can benefit and how much?
    Suppose 8 Richter scale earthquake occurs in certain place. What is the usual radius of fatal damages? Although the radius might be small for developed cities with strong building, but for weak buildings of developing countries, it could be 100s of kilometers.
     
  7. Apr 22, 2012 #6

    apeiron

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    You do get some advance warning from the faster moving, very noisy, P-waves ahead of the main S-wave shake. For an 8, that could be as much as a minute's notice.

    Not much use for a public warning system, but enough to start thinking about where you're going to dive if you recognise the signs.

    Edit: ooh, just had a 3.9 jiggler just then. :smile:
     
    Last edited: Apr 22, 2012
  8. Apr 22, 2012 #7

    Astronuc

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    That's detection, not prediction.

    Prediction infers knowledge in advance, preferably well in advance.

    USGS is working on a warning system.
    http://www.usgs.gov/blogs/features/...arthquake-early-warning-system-to-california/

    Separately, seismologists and geologists are attempting to develop predictive methodologies, but requires a lot more sophisticated monitoring and modeling.

    http://earthquake.usgs.gov/aboutus/nepec/
    http://www.ess.washington.edu/SEIS/PNSN/INFO_GENERAL/eq_prediction.html
    http://www.certifiedchinesetranslation.com/earthquake/aki00.html
    http://scec.ess.ucla.edu/~ykagan/perspective.html

    More resources
    http://earthquake.usgs.gov/learn/topics/?topicID=53&topic=Prediction
     
  9. Apr 22, 2012 #8
    Thanks Astronuc.
    But seems like the networks are still regional, not global.
     
  10. Apr 22, 2012 #9

    Evo

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    This is part of what confused me about your OP, what do you mean by "global"? These systems are very expensive, I read that japan's system cost ~one billion dollars, and not every country has problems with recurring earthquakes that would warrant such an expense.
     
    Last edited: Apr 22, 2012
  11. Apr 22, 2012 #10

    Astronuc

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    Most networks are national. Instrumentation is placed in those areas deemed to be of greatest risk.

    As Evo indicated, these networks are quite expensive. They require instrumentation and the communications infrastracture. If one reads the literature, one finds that one of the greatet challeges is 'where to put the monitoring devices' that provide some clue as to the state of the earth. Also, note that earthquakes can be a few km to several hundred km below the surface. We see typical well depths of a few km. The deepest well bore on record is only ~12 km. Ref: http://en.wikipedia.org/wiki/Kola_Superdeep_Borehole

    There exists the Global Seismographic Network (GSN) - http://earthquake.usgs.gov/monitoring/gsn/
    http://pubs.usgs.gov/fs/2011/3021/

    The US has the Advanced National Seismic System (ANSS) - http://earthquake.usgs.gov/monitoring/anss/

    One approach to placing monitoring stations would be to use hazard maps in order to locate instruments in places most likely to produce seismic events.
    http://earthquake.usgs.gov/hazards/products/ [Broken]

    However, faults are long continuous structures, and there may be numerous parallel faults in a particular seismic zone.

    To give one an idea of how complicated establishing a montoring system can be, see howhttp://www.canterburyquakelive.co.nz/QuakeMap/AllQuakesSinceSept4/ [Broken]

    The seismic activity around Christchurch was relatively quiet until Sept 4, 2010.
    http://www.canterburyquakelive.co.nz/Quake100Years/ [Broken]
    http://www.canterburyquakelive.co.nz/QuakeYears/ [Broken]

    Now it's quite active.
    http://www.canterburyquakelive.co.nz/
     
    Last edited by a moderator: May 5, 2017
  12. Apr 22, 2012 #11
    One of the other problems with such a system is that some of the areas that would benefit most from such a system don't have the infrastructure in place to make it worthwhile even if they could afford it and site everything properly.

    It is useful in a highly connected society like that in Japan where a warning can be communicated to the population quite rapidly but in a lot of other areas you simply couldn't inform people fast enough to make system work as hoped.
     
  13. Apr 22, 2012 #12
    Strange that in a thread about earthquake prediction the word "radon" gets no hits. But the radon concentration could be increasing in the atmosphere due to fissures and cracks opening, shortly before an earthquake.

    There must be something useful in this google search
     
  14. Apr 23, 2012 #13
    Note we are talking about "early warning" and not prediction as Astronuc pointed out earlier. An electronic signal travels faster than the seismic signal by some orders of magnitude. Therefore it is theoretically possible, and indeed practically possible to detect an earthquake locally and to issue an early warning to the rest of the world. A good system will respond to such a signal by shutting down power to electric trains and closing gas pipes, to limit damage when the seismic waves arrive.

    An interesting example of this phenomenon has arisen due to the rise in popularity of social networking. Some people noticed that news of an earthquake in Japan hit Twitter before it was up on the USGS website. Of course, this is because people in Japan with their mobile phones felt the earthquake before whatever seismometers are used by the USGS to auto-update their earthquakes page, simply because they were closer to the source.
     
  15. Apr 25, 2012 #14

    davenn

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    There is a global network
    LISS

    but for what you are thinking its not going to work because anyone at substantial distance isnt going to feel the quake recorded by the sensors anyway

    My system records easily records the big events from anywhere around the Pacific and the huge events world wide, BUT I am not going to feel any of them unless they are LOCAL or REGIONAL in which case the global network isnt going to give me any warning as I will feel the event well before they detect it.

    seismic wave speeds, just to set you straight....

    P waves ---- 7 to 8 km / sec
    S waves ---- 5 to 6 km / sec
    Surface waves ---- 3 to 4 km / sec

    all give or take -+ ~0.5 km / sec


    P waves are no noisier than any of the other waves generated
    That still totally depends on how far it is from you and for a local event.
    The detection of the the P wave would still have to be by sensor if the event was more than ~ 50 - 100km or more from you, as their amplitude tends to be realitively small in comparison to the S and Surface waves.
    have a look in this thread where I posted my seismogram of the Mw 8.6 Indonesian quake several weeks ago, look how small the P and S waves amplitude is compared to the surface waves.
    Indonesian event

    Its the surface waves that do the majority of the destruction. Local to the epicentre of the quake, the P and S waves are not much more than passing pulses

    cheers
    Dave
     
    Last edited: Apr 25, 2012
  16. Apr 25, 2012 #15

    davenn

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    As I pointed out in my previous post .... early warning of shaking to the rest of the world is pointless as they are not going to feel the event anyway. The warning of impending shaking needs to be where the shaking is going to occur, and if that is close to the epicentre, say out to ~ 100 km then the warning is going to be from none to maybe around 13 sec. 10 sec or so is going to give people a chance to dive for cover but those close in still wont have time to do anything

    Dave
     
  17. Apr 25, 2012 #16

    davenn

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    Radon is one useful predictor, but like a lot of predictors, it is not reliable. that is, there isnt always an increase of radon emission in the days or weeks prior to a quake.
    Most seismologists I have had any discussions with, and from others being interviewed on TV in doco's or on the new etc, pretty much agree that, in the mean time, short term prediction lies somewhere between very difficult to impossible.
    The main thrust of research these days is to come up with ways to mitigate damage and deaths. Stronger structures and retro fitting of older structures with base isolation techniques, teaching earthquake awareness etc

    Dave
     
  18. Apr 27, 2012 #17
    Obviously by rest of the world I do not mean to imply that shaking will be felt everywhere in the world.
     
  19. Apr 27, 2012 #18

    davenn

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    no probs :) I just based my comments on your wording as the Op was going down a similar path.
    Earthquake warning needs to be improved at a local and regional level. And it is really at the local level where its the most difficult. How can you reasonably respond to a situation where you have maybe less than 5 sec before the severe shaking starts. You brain processing is going to take 2 or 3 of those sec just to comprehend --- Ahhh quake alarm, and another couple of sec going --- ummm ummmm, what am I supposed to do ???? then BANG it hits

    I know some nuclear power stations have trigger systems like that. to what extent do you cut power ? over what sized region ? the power stations may be well out of the shake zone for a particular quake and you end up cutting power to 1000's of customers that wont be affected by the shaking resulting in additional disruption.
    " shutting down power to electric trains" Dunno if I would be thrilled about the train loosing power as its going through a tunnel and everything is shaking around me. ;)

    One would hope that these clowns that govern us have at least considered some of these things to see what is feasible ???

    Unfortunately I just remember all too well the comment by the then mayor of San Francisco ( when the doco was filmed) basically saying " because of financial constraints etc that would send the city broke ( when it comes to better response prepardness) we just hope that it doesnt happen on our watch" ie. leave the tough financial decisions to the next administration to worry about :(

    Dave
     
  20. Apr 29, 2012 #19
    Another Question, "Is it possible to fully know about the intensity of the Earthquake, and how far and with what force it is going to travel, just by measuring the surface shakes by a sensor?".

    I ask this because, when I am standing on the road-side and a heavy vehicle passes by, I feel shaking as much as or even more than a significant earthquake. But that quake isn't going to travel far.

    I may have used Layman terms, but I hope you can get what I am trying to ask.
    Thanks.
     
  21. Apr 29, 2012 #20

    davenn

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    no not really

    I suspect the intensity dissapates in the same or similar way to light, radio waves, sound waves .... the wavefront spreads out over a wider area and is controlled by the "inverse square law" every time you double the distance there is only 1/4 the amount of energy recorded at a given point.

    now on top of that you also have the type of ground the seismic waves are travelling through and how that type of ground responds to the shaking. In general the softer the ground the more intense the shaking.
    so for example ... take you and me we are the same distance from a M6 event, you were on soft alluvial gravels and soil (sediment) and I was on bedrock. You would feel stronger shaking than me.

    There's just so many other variables too.....
    the depth of the sedimentary layer and its distance from the epicentre of the event
    this can determine if the sediments can respond in resonance to the frequency of the seismic waves. sediments 2km deep may respond very differently to a quake at 20 km distance then they do to a M6 quake at 50km. The quake at 50 km may cause more shaking which goes against assumptions.

    Buildings and other structures such as bridges and overpasses respond differently in the same way as the ground does....

    A M6 event at say 50km distance and 2 buildings, side by side in a street, one of 4 levels (stories) the other of 15 levels depending on the frequency of the seismic waves that reach the buildings, one is resonant to the freq of the waves and crumbles down the other isnt and only suffers minor damage.

    I saw this effect when I visited Christchurch city last year after the M6.3 shook the city from only ~ 10 - 15 km distance. Buildings of similar building quality, but showing substantially different degrees of damage depending on their height. Christchurch is build on a very soft sediment basic, its basically a multiple river delta. The natural ground water level is only ~ 1 metre below the ground surface in many areas.
    Neither the ground nor the buildings could handle the intense vertical and horizontal movements, that in several areas exceeded 1G of acceleration!!!

    Another classic example of this was the 1985 M8.0 Mexico earthquake. The epicentre was 370 km west of Mexico City, yet the city was pretty much destroyed and a huge death toll. for some time seismologists didnt understand why a quake at such distance from the city did so much damage.
    Studies revealed that Mexico City sat atop of a huge and deep sedimentary basin. These sediments amplified the shaking substantially and the ground motions in the city were stronger than those recorded closer to the epicentre of the quake.

    well that was a huge write-up haha hopefully helpful in answering the questions

    cheers
    Dave
     
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