Nuclear Explosions & Seismology

On January 19, 1968, a thermonuclear test, codenamed Faultless, took place in the Central Nevada Supplemental Test Area. The codename turned out to be a poor choice of words because a fresh fault rupture some 1200 meters long was produced.
Both earthquakes and nuclear tests can rapidly release a large amount of energy. The energy source for small yield (typically less than 50 kilotons) thermonuclear devices is the splitting of heavy radioactive isotopes.
No. Even huge amounts of explosive almost never cause even small earthquakes (see previous FAQ), and it would take hundreds and thousands of small earthquakes to equal a large one, even if it could be done.
On September 10, 1996, the United Nations General Assembly voted 158-3 to approve a treaty prohibiting all nuclear tests. The Comprehensive Test Ban Treaty has been signed by 130 nations - including the United States.
Seismology is one of several fields which plays a role in monitoring the CTBT. Underground nuclear explosions produce seismic waves with unique characteristics which allow the discrimination between explosions and earthquakes.