I don't know how you prepare for something like this. Two adults and two children died when a sinkhole/landslide swallowed their house. They were watching TV in the basement.

"Their house tumbled down 40 metres into a giant crater created by the landslide, 400 metres long and 600 metres wide. The four bodies were found submerged in thick sludge in the basement. Their bodies were found Tuesday night by firefighters who scooped away the sludge by hand ..."

http://www.nationalpost.com/story.html?id=3012668

http://www.theglobeandmail.com/news/national/quebec/four-missing-in-quebec-after-home-collapses-into-sinkhole/article1564432/%3Cbr%3E%3Cbr%3E/

http://www.theglobeandmail.com/news/nati...article1565639/

http://www.edmontonjournal.com/news/Family+buried+alive+landslide+authorities/3023520/story.html