Japan's Fukushima and Miyagi prefectures were rocked by a strong 7.3-magnitude earthquake on Wednesday night, leaving millions without power and sending tremors as far south as Tokyo.

Video footage of the quake shows shaking buildings, rattling windows, power outages—and what may be the eerie, unsettling phenomenon of "earthquake lights," unexplained flashes that have been reported in the vicinity of earthquakes for many centuries.

Scientists debate about whether or not earthquake lights are a real phenomenon in their own right or if there are more mundane explanations for them—power lines going down, say, or transformers blowing.

Of course, they've been reported for much longer than their have been power lines or transformers, so that's not too terribly convincing a hypothesis.

A few years ago some scientists put together a compelling theory:

"The process starts deep in the crust, where rocks are subjected to high stress levels, prior to the stress being released to produce an earthquake," Thériault says. In certain types of rock, Freund has shown in lab experiments, this stress can break apart pairs of negatively-charged oxygen atoms that are linked together in peroxy bonds.

When this happens, each of the oxygen ions are released, and these can flow through cracks in the rock, towards the surface. At that point, the thinking goes, high-density groups of these charged atoms will ionize pockets of air, forming a charged gas (a plasma) that emits light.

Slightly less mysterious, not really any less unsettling!

Meanwhile, other users uploaded their own footage of the quake:

Let's hope the shaking is done and the ocean stays right where it is.

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