The surrounding area certainly didn't survive. The Estate seems to now be an island over Dagnor's Cauldron as opposed to in an alcove within the walls of the depression. As for Unrest itself, I can only assume that the dusty werebats that would periodically rush the hedge maze from the basement for no apparent reason had a major hand in it's salvation.
All the people stampedeing away to the old zone line screaming TRAIN! pounded down the earth so hard it became like a concrete foundation, and it stood firm while everything around it fell away into the ocean.