Of the 65 earthquakes studied, 56 occurred along an active or ancient rift zone. And 63 of the 65 quakes took place where the geological faults that ruptured were almost vertical—as opposed to the shallower angles that many major faults take.
This steep geometry could explain how earthquake lights appear, Thériault and his colleagues say. Team member Friedemann Freund, a mineral physicist at the NASA Ames Research Center in Moffett Field, Calif., suspects it all starts with defects in a rock, where oxygen atoms inside a mineral’s chemical structure are missing an electron. When the stress of an earthquake hits the rock, it breaks chemical bonds involved in these defects, creating holes of positive electrical charge. These "p holes" flow can vertically through the fault to the surface, triggering strong local electric fields that can generate light.
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The fire that is sometimes seen and experienced just before or during earthquakes could be generated by methane escaping in conjunction with positive electrical charges, which ignite the methane. Here in the La Brea tar pits and valley areas (West Los Angeles and Miracle Mile areas) there is a lot of escaping methane. I would not want to be in that area during an earthquake.