By Josh Witten | March 1st 2010 06:52 PM | 9 comments | Print | E-mail | Track Comments
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    Are you thinking about earthquakes? I don't blame you. Been an interesting arbitrarily defined start of the time unit. We've had a huge earthquake (8.8 in Chile) and a not so big, but devastating Haiti quake (7.0). Many lives have been lost or completely altered, which makes this a great time to remind you that all revenue from this blog will continue to be donated to Medecins Sans Frontieres (Doctors Without Borders) for the foreseeable future.

    Over at Florilegium, Rycharde Manne ( I have it on good authority that this is a pseudonym* - Hank strongly recommends you read the notes) has earthquakes on the brain too. So, you are in some subjectively determined quality level of company. He wondered:
    Why are we having so many earthquakes recently? . . .However, this isn't a conspiracy website, so are there any scientists in
    this field who can explain this huge spike in earthquakes? An artefact
    of more measuring stations, surely not?
    -Rycharde Manne
    Sure, I just ellipsed the entire article, but trust me, its ok. We've got the important points. The onus is on the scientific community to explain why this is not an atmospheric and communications research laser shaking the world to bits and Hugo Chavez is wrong.

    The evidence that earthquakes are becoming more common comes in the form of a graph like the one I'm showing here, based on data from The US Geological Survey (USGS). However, the data used to create this graph (and the one in Rycharde's article) are not a comprehensive list, they are:
    Selected earthquakes of general historic interest.

    This is a biased sample set. The trend is only showing that the number of earthquakes considered "interesting" increases as time approaches the present. Not surprisingly, more recent earthquakes are more likely to be of interest. It is not surprising that the USGS took down such an asinine graphic. Or, was it a cover up?

    Rycharde identifies the trend as starting around 1999. Fortunately, if you are willing to dig a little, there is good data about earthquake frequencies for the decades of the 1990s and 2000s. While more earthquakes are detected each year due to increased numbers of survey stations and technological improvements, the frequency of earthquake magnitudes is not any different. 

    Indeed, the increase in numbers of earthquakes detected is almost entirely accounted for by the detection of small earthquakes with a magnitude around 4 or less.

    Maybe it is as simple as more survey stations:
    Although it may seem that we are having more earthquakes, earthquakes of magnitude 7.0 or greater have remained  fairly constant. 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 than 8,000 stations and the data now comes in rapidly from these stations by electronic  mail, internet 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 earthquakes more rapidly and to locate many small earthquakes which were undetected in earlier years.
    When it comes to the observation of new phenomenon due to technological improvements in equipment, I like to remember my astronomy. Before the telescope, there were five planets. After the telescope, there were nine (and then eight, but that is another story); but, the planets were always there.

    These geological events can be horrific, as the people of Haiti and Chile have so recently experienced. How much more horrible is it to exploit these tragedies for political or ideological gain, or to naively provide support for such efforts. Our planet is not particularly friendly toward humans. While that risk is not distributed equally, it is a risk all its inhabitants. To suggest that these tragedies are the result of unintentional or intentional acts by one group endangering another, without a shred of evidence, is unconscionably brazen and makes me quite grumpy.

    *What is the freaking point of having an internet pseudonym that is so blatantly associated with your name, which you cleverly hide in the first line of your bio?
    Josh Witten is the internet pseudonym of Joshua Witten.

    Actually, if I was going to go for an internet pseudonym, it would be from the spectacularly awesome side of the equation, like Banjo Roksurmomanoff or the rugbyologist.


    First let me say that I think you're probably right and the increase in reported earthquakes is due to technological improvements. However, the average Joe is not asking himself about an increase in small earthquakes but rather about his perceived increase in larger earthquakes, say 6.5 and above. Frankly, he neither knows nor cares that East Nowhere had a quake that no one felt. Thanks to the scale required to show all the small quakes, your graph does not adequately illustrate the number of earthquakes of larger magnitudes. I would be interested to know the per decade number of 6.5 and higher quakes prior to 1999 and post 1999. If, for example, pre 1999 there were between 6 and 12 earthquakes per decade but 1999 to 2009 there were 18, that might be considered to be significant despite the fact that it would have little effect on the overall totals. Do you have this information? (Yes, I could find it but that would require me to do research that I can probably get you to do by annoying you by questioning your article) What are your thoughts?

    If you only look at the higher magnitude earthquakes, there have been slightly more earthquakes above 8 in the 2000s. This graph is on the log10 scale so that you can see the 8-9.9 numbers, but bear in mind this exaggerates the differences at lower values, which are still well within the normal variation.

    The very slight increase in 6-6.9 quakes is small compared to increases in "small" earthquakes such as 4-4.9. The 40% increase in total quakes is driven almost entirely by quakes of magnitude 3-4.9, which increased ~40% over this time. The changes in frequency are what one would expect from increased monitoring and changing standards, such as more carefully defining seismic readings from mining explosions.

    It should also be remembered that even talking about quakes greater than 6 magnitude as "big" is deceptive. We are talking about a huge range of forces here. The scale for earthquake magintudes is log10 for ground motion, but is effectively log32 for energy released. That means a difference of one unit on the scale corresponds to about 32 times as much energy released. That makes an 8 much much easier to detect than a 6. For reference, the USGS estimates that they now (in the past decade) have the capacity to observe every single quake greater than 5 that occurs, but only observe ~75% of those 4-4.9, and only a fraction of those below 4.

    Philosophically, it is important to remember where the burden of proof lies in this debate. The burden of proof lies with those making the extraordinary claim. It is not up to geologists (or me) to prove that nothing unusual is happening. That is the null hypothesis. I've entertained this exercise in the likely ineffectual interest of stopping bad information from spreading. It is up to those making the claim to provide proff that the phenomenon is occurring. To date, that effort has been an unmitigated failure, perhaps due to the fact that the initial observation was based on rubbish data.

    Finally, bear in mind that we have no expectation that earthquake frequencies will remain constant due to natural conditions. Even if, in the future, we observe a change in frequencies there is no reason to immediately jump to the conclusion that humans are conspiring to cause natural disasters.
    Have just read this article (on prodding from Patrick!) and have recently posted an update to the article with a new graph.

    I'd have done so sooner if I had read this when first posted, however, time is not very elastic. Anyway, considering that my original graph came from various alarmist websites I think having solved where it comes from, why it is distorted and having a more meaningful graph are all a job well done.

    And there has been an increase in major earthquakes over the last 30 years from about 108 to 150 per year (an increase of nearly 40%). Is this significant?
    Time is extremely elastic. You are just not running fast enough to notice.
    I responded to your comment and the one above in one single comment, as they addressed similar points and required a lengthy reply:
    How are you going to get a lot of hits - which I assume translates into donations - if you post all reasonable calm-mongering?

    That can be tricky, but, on the plus side, I can both live with myself and sleep at night.
    How are you going to get a lot of hits - which I assume translates into donations - if you post all reasonable calm-mongering?

    That's a very astute question.
    Fossil Huntress
    Pseudo-science. Quakery. Rugby! Josh Witten has no idea what he's talking about.... *goes to calmly make coffee and see if anyone takes the bait..."