Using ground sonar, find the tunnels,
add an aliquot of something flammable,
ignite,
wait for kaboom of stored munitions under Gaza.
The trick/danger with blowing tunnels is less with getting an adequate charge into them than with knowing where they go for sure. It would be embarrassing to the max to blow a tunnel and find out later that part of it went under your own house. Using radar etc requires that one go where the tunnel actually is and in the Israeli case some of that “place”is occupied by hostiles.
Gasoline vapors blown in by a simple fan will do the job just fine but if there is a candle burning while you’re blowing the result is gonna be disappointing.
In my neighborhood we have underground lava tubes and one of the boys learned the hard way some time back. He was trying to plug a leak in his pond and destroyed his neighbors wells. Yeah, that worked out?
The Israelis are using L-track D-9’s and power shovels to trench thru the ‘hood where the tunnels are. Uncovering the existing tunnels and making the ground too loose to tunnel in is a pretty safe, low cost, and long-term effective way to go. Remember that some of this no-mans-land country is mined and the D-9’s can deal with that. I could see turning Gaza into an island.