Japan was hit by the 8.9 magnitude earthquake at 05:46 (Japanese time) and just a quarter after many chaos a HUGE tsunami was on it's way, with 10m high waves! Entire cities were destroyed, houses/cars/ships floated away and everything was and still is a mess. There were a lot of fires and many other problems.
Japan is used to have a lot of earthquakes and they are prepared for almost everything! Cuz their country lays on a critical point, under Japan there're 3 plaices conflicted and that's the cause of those earthquakes! And if an earthquake happens in the ocean not only the ground will shake but also the water will start moving: tsunami!
Everybody is sending their prayers, loves and supports to Japan. So am I!
And still there are some massive aftershocks! Check out this site I found, it reports every earthquake happened in Japan and THERE'RE SO MANY!!!
http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/quakes_all.html