and the 4.3 is not an after shock
because the 5.9 was not the main quake

we learn from the Japan 9.0

everyone made the mistake of thinking the 7.2 Japan quake on March 9th was the main quake and the 6.0, 6.2 and the 6.1 were all after shocks
[link to www.emsc-csem.org]

now click back a few pages to see wth led up to the 7.2 that led to the 6's that led to the 9

we see on:
March 6th a 4.7, 5.1 and a 5.0 BONIN ISLANDS, JAPAN REGION, as well as two 4.8
March 7th, a 4.9, 5.0 RYUKYU ISLANDS, JAPAN
March 8th, nothing over 4.5

March 9th 2011, 2 days before the 9.0, we saw in japan
a 7.2 at 02:45 utc [link to www.emsc-csem.org]
then on the same day at 18:16 utc there was a 6.0, a half hour later a 6.2, then a 6.1 2 1/2 hours later
[link to www.emsc-csem.org]
with a bunch of 4.5-5.9 between them all

March 10th we then see a 4.9 OFF EAST COAST OF HONSHU, JAPAN
then a 4.6, 4.8, 5.7, 4.9, 5.4, 5.3, 5.3, 4.7,
with the last quake before the big 9.0 being
2011-03-10 22:44:25.0 38.85 N 143.07 E 30 mb
5.0 OFF EAST COAST OF HONSHU, JAPAN
nothing at all for that region for the next 6hrs then
2011-03-11 05:46:23.0 38.30 N 142.50 E 22 Mw
9.0 NEAR EAST COAST OF HONSHU, JAPAN

my point with throwing all this out there is that we need to stay alert to all these quakes and not assume that just because a quake might look big to us, like a 7.2 and assuming all following quakes being aftershocks
there are still bigger quakes and it all depends on how fragile the crust is in that paticular region