Hi there,
I guess you mean Nauvis instead of Earth?
There is a flag called no_spawning in each ruin with somewhere a water tile that prevents the ruin from spawning on each named (value: true) planets. I just found a ruin named swamp (file ruins/large/swamp.lua) which has some water-shallow tiles in it. I can exclude this ruin from Fulgora and Vulcanus, too. There is also a ruin called nuclearAccident (medium ruin) which contains water-green tiles. I can also exclude that from those other planets.
Generally I don't want to have this mod (and core, too) limited to Nauvis only.