Japan gets hit with small tsunami - a SIX INCH TSUNAMI?? Here's the link and the question follows...?

A tsunami is caused by the displacement of water after an earthquake in the ccean. These earthquakes are usually caused by the subduction of a plate on a converging plate boundary. Their waves can travel hundreds of km. an hour and can strech out over 100 km. However these waves are not noticable at sea in deep water as they appear to be normal waves. As it approaches land it becomes compressed and grows in height because the water is becoming shallower than the ocean where it previously travelled. This is why the tsunamis we know about are mive. If a wave hitting Japan is caused by the displacement of water due to an earthquake it is clfied as a tsunami. The size of the earthquake does not matter, just that the water was displaced. If it is a wave caused by forces such as wind then it is not a tsunami.