A weather machine or earthquake gun would be an incredibly silly, irresponsible, and have very limited practical use.
Any earthquake is just a relieve of stress, which naturally slowly forms inside the earth crust. earthquake cannot be "created", it can be only prematurely initiated - thus an earthquake machine must operate on the principles of either a directed vibration at low frequencies or a directed shock/pulse. I would compare the earthquake with avalanche or rock fall - being stationary at the certain elevated altitude, the snow or rocks are in state of metastable equilibrium, but if someone throws a small rock to the right place, this equilibrium is destroyed and the entire mass of the material slides down, thus losing the excess of its potential energy. Pretty much same way a hollow cavity under ground has its ceiling collapsing, as this ceiling is also in a metastable state under gravity - theoretically one does not need a huge energy to provoke such collapse, but only a trigger to it, say a infrasound vibration.
Of course your right and atmospheric devices have nothing to do with this.