Certain words can shake the blogosphere in much the same way earthquakes stir the planet.

A new study of word frequencies in political blogs finds that equations describing earthquake evolution fit the eruption of topics onto political blogs.

News tends to move quickly through the public consciousness, noted physicist Peter Klimek of the Medical University of Vienna and colleagues in a paper posted on arXiv.org. Readers usually absorb a story, discuss it with their friends, and then forget it. But some events send lasting reverberations through society, changing opinions and even governments.

“It is tempting to see such media events as a human, social excitable medium,” wrote Klimek’s team. “One may view them as a social analog to earthquakes.”

To see how far this analogy went, Klimek and colleagues trawled 168 political blogs in the US between July 2008 and May 2010, looking for spikes in the frequency of individual words.

The blogs came from every neighborhood of the political blogosphere, from commentators and journalists like Glenn Beck and Taylor Marsh, to civilian bloggers describing themselves as everything from “far right” to “liberal curmudgeons.”

To make sure their search wasn’t biased toward particular words, the researchers wrote a computer program to search for all possible letter triplets: aaa, aab, aac, and so on through zzz. More than half of these triplets never showed up, but for the ones that did, Klimek and company listed the days when each triplet was most common and the words they were found in.

This process left them with roughly 4,000 keywords. The researchers then searched their database for instances of those words for 30 days before and after the peak.

The types of blogosphere responses took two forms, the researchers say. Some words suddenly spiked in popularity in response to a real-world event. Sarah Palin’s nomination as the Republican vice presidential candidate was the most dramatic example.

“Indeed, aftershocks of this event are still trembling and quivering through our society,” Klimek and colleagues wrote. Because these events are triggered from outside the blogosphere, the researchers called them “exogenous.”

Other words gradually grew in frequency and then died down, like the use of the word “inauguration” in the days before and after Barack Obama took office. Such events are called “endogenous” because they seem to arise within the blogosphere itself.

The researchers found that on average, 0.2 words from within the blogosphere and 1.5 words from the outside world spiked in frequency per day. For both cases, the equation that fits a graphical plot of event frequency versus event size looks similar to the Gutenberg-Richter law, which describes the relationship between magnitude and number of earthquakes in a given region.

Events that came from outside the blogosphere also seemed to exhibit aftershocks that line up with Omori’s law for the frequency of earthquake aftershocks.

“We show that the public reception of news reports follow a similar statistic as earthquakes do,” the researchers conclude. “One might also think of a ‘Richter scale’ for media events.”

“I always think it’s interesting when people exploit the scale of online media to try to understand human behavior,” said Duncan Watts, a researcher at Yahoo! Research who describes himself as a “reformed physicist who has become a sociologist.”

But he notes that drawing mathematical analogies between unrelated phenomena doesn’t mean there’s any deeper connection. A lot of systems, including views on YouTube, activity on Facebook, number of tweets on Twitter, avalanches, forest fires, power outages and hurricanes all show frequency graphs similar to earthquakes.

“But they’re all generated by different processes,” Watts said. “To suggest that the same mechanism is at work here is kind of absurd. It sort of can’t be true.”

Watts thinks the data set that Klimek and colleagues compiled could be used to study other questions.

“Who is generating these large events? Do they happen randomly? Is there a hierarchy that you could extract in the media world, where there’s this core group of bloggers and everyone copies them? Or are they consumers and rebroadcasters of stories other people are coming up with?” Watts said. “That I think would be interesting, and might tell us something about the world that we didn’t already know.”

Image: 1) Flickr/fourpointreport. 2) Klimek et al 2011.

“The blogosphere as an excitable social medium: Richter’s and Omori’s Law in media coverage.” Peter Klimek, Werner Bayer, Stefan Thurner. arXiv.org, Feb. 10, 2011.

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