From my research into the 2011 Japan Earthquake I came across many useful, in depth resources but one that I found extremely useful is from the New York Times:
This link has a great interactive map/diagram feature that makes it easy to understand how the tectonic activity caused the devastating Earthquake and Tsunami. It is also very effective at showing clearly, the areas which were hardest hit and where the Earthquake started (Epicentre).
Although the diagrams are on the New york times website, the source is actually from the U.S. Geological Survey. So, from some more digging I found another link that had some great information on the primary and secondary effects and more on the tectonic activity.
If you're looking for factual and precise information, this is golden. On top of that, it couldn't be more place specific if it tried. Give 'U.S Geological Survey 2011 Japan Earthquake' a go into google and you'll find many more sites/ PDF files/ Power points.
For some serious diagrams check out