My sister sent the link below and was surprised that there have been over 600 aftershocks. I replied that these are only M4.5+ and early on it seemed to be only M5+. Is probably the USGS list.

I'd have to look at this again and pay mpre attention, but the M4.5 aftershocks may be occurring in little bursts with one triggering another nearby one.

Chris

• Japan quake animation