I grew up and have a house on the south boundary of Camp Shelby in the Desoto NF. If they are hammering the 155s then it can rattle the world the pictures off the walls. No idea if it could be felt for 40+ miles but if someone is sensitive enough it could be....especially if they are hearing it in that general direction.

But, it could be seismograph explosions in the oilfield areas. Is it late at night or just in the early evening?