DarkElite... Abandon your heretic beliefs. Thunders are born in the sky, when air is ionised and begins conducting electricity, which searches easiest way to ground itself, thus is brang down passing through closest (from the sky, that is highest) point it senses, straight down the earth.
Thunders striking from ground to sky? It's insane, really. Thunders strike from one part of air to another, there are even ball thunders, but I've never heard about underground thunder.
The vision of thunder is almost instant, that's why some people might think it comes from the ground... But it's simply stupid. Thunders want to ground themselves, they don't want to get up high.