Why do earthquakes produce ground light?

Generally speaking, "ground light" is also called "earthquake light", that is, the light phenomenon visible to the naked eye when an earthquake occurs. In the past, many people have seen the light on the earth, which has also been described and recorded in some historical documents and astronomical and geographical materials. However, through comparison, it can be found that although these materials record the phenomenon of terrestrial light, their records are far from each other. Among them, the most significant difference is the difference in the length of time and color of ground light appearing in the sky.