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Thread: Fewer earthquakes?

  1. #1
    resident Humboldt's Avatar
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    Fewer earthquakes?

    Quote Originally Posted by Sava700 View Post


    Something odd is happening...
    Or maybe not.

    I know jbc posted this already but it makes a lot of sense so I'm reposting it with credit to him

    http://earthquake.usgs.gov/learn/faq/?faqID=110

    Q: Why are we having so many earthquakes? Has earthquake activity been increasing?
    A: Although it may seem that we are having more earthquakes, earthquakes of magnitude 7.0 or greater have remained fairly constant throughout this century and, according to our records, have actually seemed to decrease in recent years.

    There are several reasons for the perception that the number of earthquakes, in general, and particularly destructive earthquakes is increasing.

    1) A partial explanation may lie in the fact that in the last twenty years, we have definitely had an increase in the number of earthquakes we have been able to locate each year. This is because of the tremendous increase in the number of seismograph stations in the world and the many improvements in global communications.

    In 1931, there were about 350 stations operating in the world; today, there are more that 4,000 stations and the data now comes in rapidly from these stations by telex, computer and satellite. This increase in the number of stations and the more timely receipt of data has allowed us and other seismological centers to locate many small earthquakes which were undetected in earlier years, and we are able to locate earthquakes more rapidly.

    The NEIC now locates about 12,000 to 14,000 earthquakes each year or approximately 50 per day. Also, because of the improvements in communications and the increased interest in natural disasters, the public now learns about more earthquakes. According to long-term records (since about 1900), we expect about 18 major earthquakes (7.0 - 7.9) and one great earthquake (8.0 or above) in any given year. However, let's take a look at what has happened in the past 32 years, from 1969 through 2001, so far. Our records show that 1992, and 1995-1997 were the only years that we have reached or exceeded the long-term average number of major earthquakes since 1971. In 1970 and in 1971 we had 20 and 19 major earthquakes, respectively, but in other years the total was in many cases well below the 18 per year which we may expect based on the long-term average.

    2) The population at risk is increasing. While the number of large earthquakes is fairly constant, population density in earthquake-prone areas is constantly increasing. In some countries, the new construction that comes with population growth has better earthquake resistance; but in many it does not. So we are now seeing increasing casualties from the same sized earthquakes.

    3) Better global communication. Just a few decades ago, if several hundred people were killed by an earthquake in Indonesia or eastern China, for example, the media in the rest of the world would not know about it until several days, to weeks, later, long after such an event would be deemed “newsworthy”. So by the time this information was available, it would probably be relegated to the back pages of the newspaper, if at all. And the public Internet didn't even exist. We are now getting this information almost immediately.

    4) Earthquake clustering and human psychology. While the average number of large earthquakes per year is fairly constant, earthquakes occur in clusters. This is predicted by various statistical models, and does not imply that earthquakes that are distant in location, but close in time, are causally related. But when such clusters occur, especially when they are widely reported in the media, they are noticed. However, during the equally anomalous periods during which no destructive earthquakes occur, no one deems this as remarkable.

    A temporal increase in earthquake activity does not mean that a large earthquake is about to happen. Similarly, quiescence, or the lack of seismicity, does not mean a large earthquake is going to happen. A temporary increase or decrease in the seismicity rate is usually just part of the natural variation in the seismicity. There is no way for us to know whether or not this time it will lead to a larger earthquake. Swarms of small events, especially in geothermal areas, are common, and moderate-large magnitude earthquakes will typically have an aftershock sequence that follows. All that is normal and expected earthquake activity.
    for discussion's sake, of course

  2. #2
    Resident Atheist Dan's Avatar
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    bottom line is that the planet earth is only doing what it's done for millions of years and what it will continue to do for millions more,earthquakes are nothing new.

    we survived y2k ,

    the end is not coming,

    and people need to just relax about it,

    besides ! there is nothing humans can do to effect the earth's NATURAL changes anyway !


    does **** happen ? sure
    one could get shot by a stray bullet,or killed by lightning ,or ran over by a run away bus,or whatever !

    but this fear feeding paranoia worrying about crap that's out of our control is pathetic !

    I'm glad I don't live a scared life like that

  3. #3
    Second Most EVIL YARDofSTUF's Avatar
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    Quote Originally Posted by Dan View Post
    ...we survived y2k...
    Did we? Maybe its all an illusion.

  4. #4
    resident Humboldt's Avatar
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    Seems to me that what this article spells out is why there's no reason for concern about an increase in earthquake activity...that contrary to Sava's 4 pages there ISN'T an increase in activity, just more awareness and thus paranoia about them.

  5. #5
    SG Enthusiast *cho*'s Avatar
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    Quote Originally Posted by Humboldt View Post
    there ISN'T an increase in activity, just more awareness and thus paranoia about them.
    Which totally makes sense because the same goes for violent crimes, plane crashes etc. The media outlets, such as TV, grasp on to these events and blast them almost nonstop making people think there is an increase because they are hearing more about it more often. In actuality there is no real change or there might even be an actual decrease...but of course news agencies forget to mention that tiny tidbit of information.
    "There is a big difference between breaking the law and having a law designed to break you. We will not be broken." -- Jinny Simms

    "On the street everything is legal! I don't believe in an eye for an eye, I believe in 2 eyes for an eye." -- Bas Rutten

  6. #6
    Maneater JawZ's Avatar
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    There is an increase in activity as it's all cyclic in nature. You guys keep forgetting that the numbers, even though they are cyclic, are being AVERAGED out over long periods of time. EVERYTHING can be averaged out over a long period of time...and the longer the period of time, the smaller the frequency.

    ...formerly the omnipotent UOD

  7. #7
    resident Humboldt's Avatar
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    Quote Originally Posted by JawZ View Post
    You guys keep forgetting that the numbers, even though they are cyclic, are being AVERAGED out over long periods of time.
    Known, with the assumption that most paranoia is based on a personal time frame instead of a mechanically or geologically recorded history.

  8. #8
    resident Humboldt's Avatar
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    See!! Its starting... prepare now! 2012 is right around the corner!!
    In reference to my previous post.

  9. #9
    resident Humboldt's Avatar
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    Quote Originally Posted by Dan View Post
    bottom line is that the planet earth is only doing what it's done for millions of years and what it will continue to do for millions more,earthquakes are nothing new.

    this fear feeding paranoia worrying about crap that's out of our control is pathetic !

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