There’s often some sort of lightning discharge when earthquakes are occurring; don’t know if anyone has figured out precisely why, I’ve heard some say the compression of minerals in the ground causes the generation of an electrical field.
Here is a surveillance camera video which caught the Napa California quake of several years ago with accompanying light discharges:
https://www.youtube.com/watch?v=RknvjVTCFhM
Either that, or that is simply the flashes of electrical systems shorting out, from the quake.
One of those.
:)
Most of those flashes I would attribute to line-to-ground faults on overhead power lines or transformers or surge protection fuses blowing. Simple overcurrents in the electrical distribution system power lines faulting, either phase to phase or phase to ground.
There might be issues associated with grinding rock materials, changing dielectric constants of the materials and then allowing normal ground currents to form, then arcing in unforeseen fashions.
There might be some esoteric particle physics occuring associated with gravitons and photons and electrons, but I don’t believe there is any technology to support those more sophisticated notions.