I was sitting on a wicker couch in the screen porch, (North Jersey Coast). My lab, Millie, loves to go in the back of the couch and rub against the wicker using the wall to push off, so when the couch started to move back and forth, I called out to Millie knock it off, but then I realized she was up on he couch with me, I got a little nervous ... what the h&%$ is under me. Then it stopped, very strange feeling, Millie looked up at me and then went back to sleep. Waited for an after shock, didn't happen.