You can use dynamic paint with scaling torus-mesh as a brush like here http://vimeo.com/38450564. Just uncheck dissolve button.
I tried to use another way - plane with wave modifier as brush for “padre” displacement, but it seems it doesn’t affect “padre”. Hard to say if it’s a bug or too much combinations sometimes I have problem to let dynamic paint work in this Bmesh build. Usually I switched to edit mode and back, it helped me. But not now.
Totally first idea was create very specific animated texture via dynamic (tune it via nodes) and later use it as texture for displacement modifie, but modifiers doesn’t support image sequences in textures.