Aftershock? Or separate event?
Since there have been many quakes in the same location today yet they are only about a hundred miles away from the 9.0 quake, it's possible that they are after shocks.
From my living experience in California, seismologists find the answers sometimes weeks after such events. The relevance though of whether they're after shocks or separate events is if they occur on a newly discovered fault.
After shocks often cause as much damage as the initial quake.
Seismologists have predicted the possibility of tsunamis in the area from after shocks for up to a year from now.