Toby mentions the possibility of a megaton blast. A megaton is equivalent to 1,000,000 tons of TNT. For reference the bomb dropped on Nagasaki was a 21 kiloton yield equivalent to 21,000 tons.
It is interesting that the team doesn't have a Shop Vac to pick up the dirt/debris after the quake. However, even if they had a Shop Vac, they were without sufficient power to run one. All the items powered in the final scene are either battery powered camping lanterns or the hand cranked radio Toby complains about.