It's original use is to use the earth as your weapon, this was the original intent;
I came up with a book list that outlined all the powers, though an old fan of the RP wanted help out so he wrote out the notes for each book; I've updated the list today.
It's something I need to edit out when I get home from work, but the fan who wrote up the list watched 'avatar, the last air bender' and got the sonar idea from Toph, whoever the blind earth bender was. She couldn't see so she used the earth to help her grasp what was around her. Only problem with doing this however, she couldn't hit airborne opponents.