John or others: Could the quake have ruptured an area equivakent to a M9.5+, but have been a little slow, so that the energy release was only that of a 9.0? The way I understand it...and not my field, is that the 1946 Alaska earthquake was a tsunami earthquake with a M7.3 or something (on the link I made the other day to 35 m tsunami at Dutch Harbor lighthouse). That if the motion is just slightly slower than usual the seafloor has better coupling to the water (I'm partly guessing here...).
Also, if what I suggest is possible, might the slips have been larger than they have been getting in the source modeling?

Someone, probably Mark Legg, suggested that the M5 something 1981 Santa Barbara Island California right-lateral earthquake on the San Clemente fault system might have been slow...because aftershocks were spread along the fault in a much larger area than would be expected by the magnitude....
Chris