Has the 121 sq miles that is Gaza, started settling yet, from all those blown-up, collapsed tunnels?
I wouldn’t expect the whole place to collapse; even large tunnels are small by comparison to an area measured in square miles. The problem is, you don’t really know where the tunnels really are. You don’t know where a collapse is likely.
In parts of West Virginia, homeowners can get “mine insurance”, to cover the possibility of an old, poorly mapped underground coal mine collapsing under their property.