>> what happened in japan was a subduction zone earthquake which created a magnitude 8.9 event which propagated a lot of energy into the shore there. creating a tsunami that you've seen all sorts of information an videos on and provides a lot of damage onshore. >> is there any way, it's like asking what caused this weather. what causes an earthquake? what is the most basic -- give me a basic primer on that. >> basically what you see happening here is that there's a subduction zone. we've got two plates moving together. one under the pacific ocean, diving underneath japan, sliding down underneath japan. it has to break every once in a while and that is a very large event which occurs on several hundred year recurrence intervals, but this is something that's not unexpected to happen in the long term. >> i've got relatives that live