>> i can't say specifically for japan, but i do know that the geologic record shows that back in 800 a.d. there was an earthquake very much like this one and the geologic record shows that a very similar scenario had played out in this location. but 800 a.d. is a very long time ago. and, of course, there would be very little human record to show for that. >> marcia, with that, we'll leave it there. thank you very much indeed for joining us. your expert on the subject this evening. in a moment, images from inside japan's biggest ever earthquake by the people who lived through it. ♪