Glen, The only 2 seismologists who post here are John Vidale and Roger Hunter...John does not post here much, and Roger's interests seem to be more on evaluating prediction. So, you may know more about some of these subjects than anyone here except John. I need to read more papers, but need to read on such subjects as paleoclimate, Los Angeles region sedimentation and basin modeling. Lowell Whiteside introduced me to this page and he was ahead of the curve on distant triggering...he sent me a copy of his U. Colorado comps paper back in 1990, which discussed this....2 years before Landers made it evident. I've never had anyone on this page dispute my comments like...in 1990 most seismologists would have thought distant triggering (P and S wave) would be nonsense...and I don't think there was much work on more distant stress transfer. As for M4s...depends on your context. If you are predicting M4s in areas that have them daily, then not an interesting prediction...if in areas where they lack, then interesting. And, as you say, they all tell you something...well-located M2s in southern California can help us map the deep structure of faults. M3s with focal mechanisms can tell us about the slip. M4s in stable continental areas may help set earthquake insurance rates, and affect whether I would bother getting it or not..
Chris