It is obviously true that the atom bombs were dropped on the Japanise cities. However I'd bet next months salery on the fact that the seismic trace from an atom bomb is very different from that of an earth quake. At this point I would like to point out that I am not a geophysics expert and I am more than happy to be corrected.
However I do know that with a natural quake it is usual to get smaller seismic waves before the big one, that would not be the same with an atom bomb. You would get a large explosion, followed by the earthquake. Atom bombs and H bombs have a highly characteristic 'pulse' pattern. There is a world wide net work that monitors for them.....that is how nuclear proliferation is monitored
The americns could not possibly hide an atom bomb going off, unless every monitoring nation colluded with them......and that monitoring is done by the Russians, the US, the UK and many other countries.
So unless the whole developed world is helping the US to cover up, this conspiricy is a pile of horse shit.