Hi Glen - You write that "Roger has given a well founded basis (mathematically) for . . . seismicity in north lat versus south lat." However, at the time you posted, Chris had already supplied what seems to me a good answer. And I haven't seen Roger's explanation . . . Anyway, were you surprised somehow that there were more M7 quakes in the Northern hemisphere? For the reasons provided by Chris, that result should have been obvious going in. I guess I'm rather confused by the whole point to the original request for Roger's analysis. It seemed, at first, that you were not attempting to distinguish between northern and southern hemispheres, but, rather, between incidence of large quakes, in any particular hemisphere, during periods of aphelion versus perihelion. An analysis of THAT result might, possibly, have been of some interest.

And, also, in your original post, you state that the question has to do with planetary physics, which doesn't seem to make sense. The gravitational interactions between bodies are already well understood. The answers to your original request would bear mostly on geophysics and seismology, no? And, in fact, you seem to state as much in the post above, where you say it (differences between M7 occurrence in North v. South latitudes) is an "earth science finding."

Also, a minor quibble. An earthquake does not have a "strike." You've used that term before, in the same context, and I think I know what you mean. As I believe you know, a quake has a "focal mechanism", which refers to the actual first, relative motion of the faults. The horizontal component of that motion, if any, occurs in one of the two directions of the strike of the fault involved.

Michael Williams (I am not a seismologist, geologist, or any othe "ist")
Arroyo Grande, CA USA