Earthquake Lights

These are mostly white or bluish flashes that precede large earthquakes and last for several seconds. They have been reported infrequently for hundreds of years, according to the U.S. Geological Survey.
It wasn't until the 1960s, when people took pictures of this phenomenon during the Matsushiro earthquakes, that the scientific community started to take it seriously.

Earthquake lights are caused by an unknown mechanism. There are numerous theories as to how and why they occur.

One explanation involves intense electric fields created piezoelectrically by tectonic movements of rocks containing quartz.

Another possible explanation is local disruption of the Earth's magnetic field and/or ionosphere in the region of tectonic stress, resulting in the observed glow effects either from ionospheric radiative recombination at lower altitudes and greater atmospheric pressure or as aurora. However, the effect is clearly not pronounced or notably observed at all earthquake events and is yet to be directly experimentally verified.