Energy in a tsunami vs. energy in a hydrogen bomb

A popular CT says that Russia has built nuclear torpedos for devastating coastal areas by generating a man-made tsunami with an underwater fusion device.

Is it possible? Let's compare the energies.

[link to www.scrivial.com (secure)]

"...huge tsunamis like the Sumatra tsunami,2004 has energy of order 10^17 Joules. Several including National Geographic [Link] and USGS websites states that it is about 20x10^17 Joules, an equivalent of 23,000 bombs, the one that was dropped on Hiroshima. That’s huge! To verify ourselves, we contacted the U.S. Geological Survey (USGS) and asked them. B.Kelly, from USGS said that there is a slight mistake - it is equivalent to 23,000 bombs that was dropped on Nagasaki (20KiloTNT) not Hiroshima (15kiloTNT)."

So, in order to generate a tsunami the size of 2007 Sumatra tsunami, the nuclear device would have to have a yield of 23,000 * 20 kT = 460 MT.

The largest fusion device ever detonated was the Tsar bomba with a yield of 50 MT, and a designed maximum yield of 100 MT, and it was bulky as hell. Fusion devices can be scaled up indefinitely by adding more fuel (=hydrogen or its isotopes), but it will increase the size of the device. The yield does not increase in a linear proportion to the amount of fuel, but if we assume that it did, the size of a tsunami generating torpedo would be about ten times the size of the Tsar bomba. That would make it about the size of a modern boomer.

Ok, so the size becomes impractical, but of course the "crazy Russians" could have converted their old boomers into remotely controlled tsunami bombs. However, it is not obvious that a nuclear detonation would actually generate a tsunami. Tsunami waveform is special, because it is created by the sea floor lifting up and pushing water up in a linear fashion. Tsunami is not just a surface wave, but it extends from the bottom of the sea to the surface.

An underwater nuclear detonation, on the other hand, will create a superhot bubble of vaporized water (the vaporization will actually eat up a lot of bomb's energy, but let's ignore it), which will then burst to the surface while the bubble will collapse on itself. Yes, it will generate a wave, but since the initial pressure wave will be radial instead of a linear, followed by a rush of water filling the bubble, the waveform will certainly be different.