Do some research and you will discover what I am saying is true. 
I did some research and discovered what you are saying couldn't be any further from true. Calling it flat out wrong would be an understatement.
Firstly, a nuclear bomb releases a minute fraction of that of a tsunami causing earthquake. The two aren't even comparable. That is fact. Now you are trying to say that since it would be occurring around a fault line, the nuclear explosion would somehow spur a chain reaction which causes an actual earthquake. I knew this to be complete hogwash as soon as I read it, but decided to pull some facts up just to back up what I already knew:
An earthquake is the sudden release of strain energy in the Earth's crust (see "Earthquakes in a Nutshell"), but strain builds up from several different causes: the movements of plate tectonics, the weight of sediments shifting from erosion or from deposition, changes in fluids underground, and more obscure factors like mineral phase changes in the mantleSo the forces that ordinary bombs exert don't cause earthquakes. The amount of energy in bomb explosions is microscopic compared to the energies of earthquakes. It's like the difference between playing on a piano and dropping the piano down a flight of stairs. Secondly, the existence of a fault line/zone is nothing more than an area where the earth releases internal strain from its crust (earthquakes). A bomb has absolutely no impact on strain/movement of plates/weight of sediment/erosion/changes in fluids and absolutely zero effect. You could detonate a hundred nuclear bombs simultaneously right on top of a fault line and it would not initiate an earthquake, the two have nothing to do with one another.
And Chalenge in regards to this:
@Grizz
One advantage to dealing with ridiculous responses like yours is there is never any substance to anything you offer.
You didnt even bother to look into the possible repercussions but it doesnt matter. I have doubts the politicians in this country will ever allow a nuclear device be used for this.
It isn't my responsibility to do this research because I'm not the one saying this:
The problem with a nuclear device is that it would remove so much solid material that it would cause a monumental movement of millions of tons of water below the surface. At that depth pressures are so high that the resulting shock wave would be carried not hundreds but thousands of miles like the worst tsunami imagineable.
Stick to flight sims and scorpion bite antidotes.

Not that this matters anyways. The main point is being lost in all of this. It would still probably be a bad idea to use a nuke for many of the reasons oneway pointed out.