What would exploding a nuclear device on the surface, or even underground (using those fancy ground-penetrating missiles, by the san Andreas Fault do? The unrealistic movie Superman notwithstanding, I have several theories:
- Nothing except vaporize a few people within the vicinity. Earthquakes are caused by tectonic plate shiftfs, and exploding a nuclear device doesn’t mean the plate is going to rub against the next one.
- Create a big earthquake. Tectonic plates are always rubbing against each other, but don’t move beccause of friction. A nuclear detonation would help the plates overcome their inertia, causing an earthquake of a good magnitude.
- Cause THE BIG ONE, with volcanic eruptions from magma coming up thru the damages plate edges.