Its no secret that tsunamis can be created by nuclear and other weapons. Even small yields can shift tectonic plates which in turn will cause earthquakes then tsunamis. The nuclear power plant in Japan is about to have a meltdown and most likely would mask any evidence of a nuclear detonation underwater that may have caused the earthquake just recently.

Project Seal ( also known as the Tsunami bomb) was a programme by the New Zealand military to develop a weapon that could create destructive tsunamis. This weapon was tested in Whangaparaoa off the coast of Auckland between 1944-1945. The experiments were conducted by Professor Thomas Leech. British and US defence chiefs were eager to see it developed and it was considered as important as the atomic bomb. The weapon was only tested using small explosions and never on a full scale. If it were to be fully produced and used, it would have created huge amounts of damage to coastal cities.

Internet site reference: http://www.abovetopsecret.com/forum/thread673758/pg1