Would a tsunami overturn a ship like the QE2?
Not if the tsunami caught the ship in mid-ocean. The wave-height of a tsunami in deep water is on the order of 1 meter. It’s wavelength is very long though and the phase velocity is fast, so that 1 m of height represents a huge amount of energy. A tsunami only builds up to significant heights very near shore, and mainly then very near the epicenter. Search youtube or google/video and find video of the Sumatran tsunami a few years ago hitting Phuket and Sri Lanka. It wasn’t this crashing wall of water, it was a huge fast inrush of water like the biggest nastiest tide you ever saw. However, offshore, probably thousands of boats rode through it without noticing it very much. The real danger to ships in mid-ocean are rogue waves. Those can appear almost out of nowhere. However, the danger from rogue waves is not so much capsizing a vessel as breaking it in two.
