The quake today was on almost the exact same location as the main shock on 3/11/11.
So it was just a very late aftershock of the Tohoku quake, and not enough tension is built up there to produce a M9.0.

BTW, what many people STILL don't seem to get: A M9.0 is 1024 times stronger than a M7.0, so you can't really compare them even if the numbers seem close.