Chris;

I looked at all NEIC quakes from 1973-2010 with mag 6+.

There were 4996 of them so far.

Then I called each 7+ quake a main quake and looked for aftershocks of mag 6+ within 100 km and 14 days.

There were 502 main quakes and only 176 of them had such aftershocks.

If you wish to redefine the aftershock definition I can rerun it however you wish. Just let me know.

Roger