Shout out to @COUGARACE for this suggestion.
I'd never heard of this before but evidently this is a phenomenon that has been reported by witnesses for centuries.
CNN - Reports of “earthquake lights,” like the ones seen in videos captured before Friday’s 6.8-magnitude earthquake in Morocco, go back centuries to ancient Greece.
These outbursts of bright, dancing light in different colors have long puzzled scientists, and there’s still no consensus on what causes them, but they are “definitely real,” said John Derr, a retired geophysicist who used to work at the US Geological Survey. He has coauthored several scientific papers on earthquake lights, or EQL.
Earthquake lights can take several different forms, according to a chapter on the phenomenon coauthored by Derr and published in the 2019 edition of the Encyclopedia of Solid Earth Geophysics.
Sometimes, the lights may appear similar to ordinary lightning, or they may be like a luminous band in the atmosphere akin to polar aurora. Other times they resemble glowing spheres floating midair. They may also look like small flames flickering or creeping along or near the ground or larger flames emerging from the ground.
Friedemann Freund, Derr’s collaborator and an adjunct professor at San Jose University and a former researcher at NASA Ames Research Center, has come up with one theory for earthquake lights.
Freund explained that when certain defects or impurities in crystals in rocks are put under mechanical stress — such as during the build-up of tectonic stresses before or during a major earthquake — they instantly break apart and generate electricity.
Rock is an insulator that, when mechanically stressed, becomes a semiconductor, he said.
“Prior to earthquakes, huge volumes of rock — hundreds of thousands of cubic kilometers of rocks in the Earth’s crust — are being stressed and the stresses are causing shifting of the grain, the mineral grains relative (to) each other,” he added in an interview via video call.
“It’s like switching on a battery, generating electrical charges that can flow out of the stressed rocks into and through unstressed rocks. The charges travel fast, at up to around 200 metres per second,” he explained in a 2014 article for The Conversation.
Other theories about what causes earthquake lights include static electricity produced by the fracturing of rock and radon emanation, among many others.
Keep the suggestions coming. Keep them classy. No butt stuff.