[yena]

It's not normal at all. Something was building up

[ars]

From http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usc0...

"The March 11 earthquake was preceded by a series of large foreshocks over the previous two days, beginning on March 9th with an M 7.2 event approximately 40 km from the March 11 earthquake, and continuing with a further 3 earthquakes greater than M 6 on the same day."

[mkramlich]

I strongly suspect it's related to the strange stories we've been hearing about a so-called Monster Island.

[wisty]

I think it's the other way round. An 8.9 takes a long time to build up. When it's almost ready to pop, then a smaller earthquake can set it off.