Donald, sounds like you are familiar with subductions zones, and more familar with this area than I am. I don't have an opinion about the "trading of seismic energy", as this is unclear, but I would not have a big problem with large (M7+) quakes on one part of a subduction zone having some affect on quakes on another part of the same zone within 1000 km or so-maybe farther. I don't have real evidence for this, it just sounds reasonable. Chris