Just an FYI, this requires an flying mount to do.
Okay, so there is one part of dalaran, if you mount under the archway going to krasus landing (as shown Here as the red dot) If you move back and forth underneath the archway into dalaran and back, you'll make the ground shake!
One little thing through is that it only works in about an ~50 yard radius through, aka range of an person can target / see you. But I'm assuming its far enough to annoying the people just landing in dalaran / middle of it.
You'll know its working when you get the warning that you'll be dismounted from your flying mount, just make sure your always on the ground with your flying mount and you go back under the archway after getting the warning to clear the debuff off, so you can do it again.
EDIT: Here is an little path to show you how to get it to constantly spam, just be on your flying mount and follow that path.