Roger, it looks like there is a 2 deg or more latitude shift on your plot....events are too far south by that much.

One science thing that seems clear on your plot is that the Sept 2007 quakes did not seem to increase M5+ quakes north of the equator...they had been ongoing since 2004. Please make a less terse post explaining what the parameters of your plot are....useful to me but also to others reading this.

I'm also surprised that your plot does not show M5+ quakes north of 3 deg N or so (5 deg N after correcting for problem?). Since the whole area ruptured I would expect m%+ farther north: in fact, I recall that there were aftershocks farther north.

So, something is wrong with the data base you used and/or the plot.
Chris