In 1923, Tokyo was hit by a strong earthquake that remained the strongest quake ever recorded in Japan. It was 7.9 on now obsolete Richter scale with its focus deep beneath Izu Ōshima Islands.It remined so until yesterday. On March 11th the ground deep in the ocean trembled and sent waves of tremors, and what's worse, real waves towards the land. In 1923 Tokyo paid a hecatomb mainly because of panic and really bad planning system in the military base where people sought the shelter. Gasoline tanks were also there. Tokyo was mainly wooden back then, so I think everyone can tell the rest.
In case of deep-focus, under-ocean quakes, the impact of actual trembling is not that big. The most disastrous thing is tsunami sent by such deep quakes. Tsunami leaves nothing on its way. Literally it means "port wave", and there is a wisdom in it. Tsunami on the plain ocean/sea surface is invisible, but the energy generated by such strong trigger changes the parameters of oscillations. The power and difference in the wave's amplitude and also the change in the terrain (getting higher) leads to "magnifying" the wave. This is why tsunami is called "port wave", because it is only visible when closing to the land.
And something for watching or reading:
Video:picture: AP
