In case you haven't heard the news, Barcelona fans were very happy when their team improbably cheated their way to an historic upset over Paris Saint-Germain in the Champions League. So happy, in fact, that their reaction registered on a nearby seismometer.
How do I know this? Because basically every freaking soccer publication wrote about it. "Barcelona celebrations at the Nou Camp after historic victory over PSG caused an EARTHQUAKE," shouted the Sun, for example. Or take the Mirror's headline, "Barcelona celebrations cause an EARTHQUAKE after dramatic Champions League comeback against PSG," apparently adhering to a national style guide that mandates the word "earthquake" must be written in all-caps.
This isn't the first time sports fans are supposed to have caused an earthquake. Seattle Seahawks fans set off a quake on several occasions, including Marshawn Lynch's infamous Beast Mode run. Last year, Leicester City fans caused an earthquake after beating Norwich (of all teams) on their way to their miracle title run.
I don't know much about earthquakes, but I've seen some photos. Whatever these fans might be doing to our precious planet seems a bit different than the event that tears highways out of the ground.
To find out more, I spoke with Jordi Diaz, senior research scientist at ICTJA, the research institution that registered the Barcelona "earthquake" last week. What, exactly, is going on here?
Basically—and these are my words, not Diaz's—the whole thing is kinda bullshit. It's a pretty classic "if a tree falls in the forest"-type deal. If a stadium has a seismometer near it, it'll probably register an "earthquake."
In order for a seismometer to register crowd movements—which Diaz says is "not unusual"—it has to be located within a few hundred meters of the crowd, or about as far as you could hear such a crowd. "What we record in fact is the earth shaking," Diaz wrote to me via email, "that is, the ground vibration generated by some kind of source and then traveling across/along the Earth. In our usual work, we deal with vibrations generated by natural earthquakes. In the case of the 'footquakes,' the origin of the vibration is a lot of people jumping simultaneously. In other cases, we use small explosions or even just hammers hitting the soil to produce controlled sources of vibration."
Wait, what? This is the same thing as just hitting the ground with a hammer?
Basically! Diaz says that referring to all of these things as an "earthquake" is a "language license," although they are all caused by the same resulting seismic waves. Still, you can get the same effects by having a bunch of kids jump up and down, as he often does when visiting local schools.
In order for a fan base to register an earthquake, the number of fans is obviously important, but so are other factors such as the geology of the area, the presence of other sources of vibrations (such as traffic, railways, and wind), and, most importantly, the distance between the stadium and the seismometer. Leicester City was able to record "earthquakes" despite its small stadium capacity of 33,000 because a local primary school 500 meters from the stadium had set one such instrument up.
Likewise, the Beastmode run in 2011 registered on a Pacific Northwest Seismic Network (PNSN) station a block from the stadium. (You're likely to hear much more about the Seahawks fanquakes in the future, because in January the PNSN installed seismometers in the stadium itself at strategic locations.)
Obviously, most earthquakes can be felt much farther away than a few hundred meters. To illustrate just how much more powerful real earthquakes are than fanquakes, Diaz tweeted a comparison between the Barca quake and a 4.2 magnitude earthquake in Navarra 350 kilometers away, as measured from the same location. Keep in mind that the Barcelona quake, in red on the graph, was 700 times closer than the earthquake in Navarra.
"As you can see," Diaz wrote, "even a rather distant and small earthquake results in much more energetic waves than 100,000 guys jumping just beside the seismometer." Large earthquake events are usually defined as 6 or more on the Richter scale (which is logarithmic, meaning each whole number increase is equivalent to ten times the amplitude and, thus, 31 times the energy). Diaz estimated the Barcelona fanquake was somewhere between .5 and 1 on the Richter scale.
This isn't to say fanquakes aren't neat in their own way, especially as an educational tool for kids. It's really great that a bunch of kids in primary school in Leicester wanted to record the Earth's vibrations as a result of their local team. Science rules!
If Diaz can get a few kids interested in science by telling them Barcelona fans started an earthquake, then it's a victory for science, for sports, and for all of us. Same goes for the PNSN, which now gets to study earthquakes in a relatively predictable environment, something that is normally impossible for seismologists. Hopefully this will provide some help when the really big one finally comes and destroys the entire Pacific Northwest.
"The 'footquakes' are amusing to identify and useful to reach the public attention," Diaz summarized, "but in fact they only show how powerful real earthquakes are."
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