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Back in May I posted a story about the discovery of changes in the Earth’s ionosphere leading up to the catastrophic Japanese earthquake (and subsequent tsunami) of March 2011. A research team led by Dimitar Ouzounov of the NASA Goddard Space Flight Centre found that…

…before the M9 earthquake, the total electron content of the ionosphere increased dramatically over the epicentre, reaching a maximum three days before the quake struck.

At the same time, satellite observations showed a big increase in infrared emissions from above the epicentre, which peaked in the hours before the quake. In other words, the atmosphere was heating up.

Last week an independent paper offered support for this ‘warning signal’ for massive earthquakes. According to the American Geophysical Union blog, geophysicist Kosuke Heki of Hokkaido University in Sapporo, Japan, has reported the same suggestive buildups of electrons in a new scientific paper:

“The claim that earthquakes are inherently unpredictable might not be true, at least for M9 [magnitude 9] class earthquakes,” Heki writes in an article accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

The study suggests that the total electron content, or TEC, in the ionosphere starts increasing as much as eight percent above background levels prior to massive earthquakes, with the biggest effect above the rupturing fault. The electron buildup before the Japan earthquake started 40 minutes before disaster struck.

…Days after the devastating magnitude 9.0 Tohoku-Oki earthquake struck Japan, Heki downloaded data from satellites that are part of the GPS Earth Observation Network. He was interested in oscillations of the TEC when acoustic waves echo from the epicenter into the ionosphere.

“I thought I’d see a very strong signal after this earthquake,” Heki says. “And in the course of working on that, I found something strange happened.” The TEC was higher before the expected oscillations occurred than it was after the oscillations, so he took another look at the raw data from the GPS satellites.

…But changes in total electron content aren’t rare, Heki says. Solar flares and other ionospheric disturbances can cause fluctuations. So he looked at TEC prior to other major earthquakes, including the 2010 Chile earthquake.

“I saw almost the same signature as the Tohoku earthquake,” Heki says. And although there were fewer GPS stations operational during the 2004 Sumatra quake, those showed a similar TEC anomaly. Smaller quakes, around magnitude 8.0 and below, don’t appear to have the same TEC increases.

You can download Heki’s paper from his website (PDF download).

There appears to be some difference between the two papers regarding the maximum TEC in the ionosphere, with Heki’s saying it started 40 minutes before the earthquake, while Ouzounov et al’s paper put the timeframe in days. Neither paper references each other though, so perhaps Heki did not analyse the days in advance of the quake, but only the immediate hours surrounding it? In any case, fascinating insights into the invisible earth changes that take place when a major geological event occurs.

And as I mentioned in my previous post, could these changes be responsible for (oft-ridiculed) reports of ‘earthquake lights’? Coincidentally, on the same day I came across the above news, I also stumbled across this podcast interview with David Brumbaugh, director of the Arizona Earthquake Information Center, discussing all the suggestions for a mechanism behind the anomalous phenomenon:

It’s a bird, it’s a plane, it’s… an earthquake? by Scienceline

What do you think? Is there a relationship between the changes in the ionosphere and the mystery of earthquake lights?

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