From videos online so far, it seems the strength of the quake didn't translate to massive lateral movement. There seemed to be lots of intense P-wave wiggling and bumping rather than large S-wave swings back and forth. The big Japan quake was one of those, where you saw offices being slid back and forth and everything flying off shelves.
Not sure what that means for the tsunami - but so far it seems less intense than the 8.8 would imply.
Japan uses a scale that measures the movement[0]. Of course depending on where you are the result changes, but it's a lot more usable for the practical "how much shaking will be involved here/was involved here".
Not sure what that means for the tsunami - but so far it seems less intense than the 8.8 would imply.