It shows as such on the quake animation map mentioned by Chris,

http://www.japanquakemap.com/

It does not show on the USGS 8-30 day page as I believe those are reviewed quakes, whereas the 0-7 day page is raw and not necessarily reviewed.

In fact, the 8-30 day page does not show ANY aftershocks for nearly 17 hours!!!

http://neic.usgs.gov/neis/qed/

The PDE catalog shows the quake as 7.9, occurring

FILE CREATED: Wed Mar 23 03:39:49 2011
Global Search Earthquakes= 3
Catalog Used: PDE
Date Range: 2011/03/11 to 2011/03/12
Magnitude Range: 7.0 - 9.9
Data Selection: Historical & Preliminary Data

CAT YEAR MO DA ORIG TIME LAT LONG DEP MAGNITUDE IEM DTSVNWG DIST
PDE-Q 2011 03 11 054624.62 38.30 142.34 32 9.0 MwUCMT .CM .T.....
PDE-Q 2011 03 11 061540.88 36.18 141.17 39 7.9 MwUCMT ..M .......
PDE-Q 2011 03 11 062550.79 38.06 144.60 21 7.1 mbGS ... .......

[the following is a link to search the catalog for all quakes on March 11th of mag 7+]
http://neic.usgs.gov/cgi-bin/epic/epic.cgi?SEARCHMETHOD=1&FILEFORMAT=4&SEARCHRANGE=HH&SYEAR=2011&SMONTH=03&SDAY=11&EYEAR=2011&EMONTH=03&EDAY=12&LMAG=7.0&UMAG=9.9&NDEP1=&NDEP2=&IO1=&IO2=&CLAT=0.0&CLON=0.0&CRAD=0.0&SUBMIT=Submit+Search

Brian