It's a ground version of the air sweeper that sends shock waves under the earth. The waves push ground troops back further away from the tremor shocker. Doesn't affect air troops.
Enough to disrupt the troops from attacking the building they were stood next too. Wouldn't be that good against the likes of archers or wizards but anything that needs to be stood next to the building would need to get back into position to start attacking again. Not sure the specifics on how far they would be pushed, I'd leave the specifics to supercell. Perhaps allow it to be 360 degrees but it takes 15/20 seconds from first troop detection to fire. You can see it building up enough energy to fire and hopefully your troops get to it before it happens. More defending nuisance than brilliance. It would be good if the buildings, trees and the like rocked up and down as the tremor went underneath it and returned into position after it had passed.