From the submitted link, as I see it at this moment: "This earthquake can be considered an aftershock of the March 11, 2011 Mw 9.0 Tohoku earthquake. The aftershock sequence of that event has been ongoing since March 11, and has included 58 earthquakes of M 6 or greater up until April 7 2011, two of which were greater than M 7 (M7.7 and M7.9, both on March 11)."

I'd hesitate to say 'just', and there is a rigorous definition of aftershock that this may or may not fit, but it's very close to the big one last month and certainly related to it.

So I'd go with 'yeah, basically' in the absence of a seismologist telling me otherwise.

In January there was a 6.9 quake here in Chile, and seismologists said it was an aftershock of the big earthquake of one year earlier. For what I recall, any earthquakes within a couple of years of the big one are most probably aftershocks.