The type caused by (fill in the blank) (fill in the blank) below surface. I believe geologically and engineering wise hamas recent collapses may be related to urban activities up on surface. Traffic and construction. From what I have seen in photos the tunnels are not carved out solid limestone but a packed congomulate of sand,stone and clays hence the cement bulk work shoring. Vibration man, good vibration.

Maybe Israel should do nothing and wait for Czar Vladimir the First to ride in with his Cossack hordes and save the day, just like he's doing in Syria.

HOW FAR ALONG? DETECTABLE FROM SPACE? DESTROYABLE BY BUNKER BUSTERS? PUT MORE EFFORT INTO IT!