How Earthquakes Make Spacewaves

But up in space, strange things were going on. The acoustic waves generated by the quake just got bigger and bigger as they moved up.

The air is so thin in the upper atmosphere that "the wave gets amplified," so it doesn't require much energy to cause a ripple in the ionosphere, which circles the earth at between 45 and 620 miles up, Artru says.

"A displacement of one millimeter on the ground can cause a displacement of 100 meters in the ionosphere," she says. So a tiny pressure wave gets amplified so much that it's huge by the time it gets about 50 miles above the ground.

When the shock waves reached the ionosphere, they caused some of the electrons to rearrange themselves, influencing the time it took for the signals from the GPS satellites above the ionosphere to reach the Earth below.

The result, according to the European Space Agency and Artru, was a very weak, but very distinct, pattern of interference that could only have been caused by acoustic waves generated by the earthquake.

Space Weather Watch Ahead?

Artru has since repeated the experiment with a magnitude 7 earthquake in Japan and got the same results, although the signal there was less clear.

She suspects the system will work only on major quakes, but it may be useful for several other purposes. Even ocean waves generated by a huge quake should send up pressure waves, so it might someday be possible to track waves generated by a quake.

That's a ways off, she says, and it may not even be practical.

But she's proved her point, paving the way for the European Space Agency to launch an international program aimed at detecting changes in "space weather" and their possible impact on planet Earth.

Lee Dye’s column appears weekly on A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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