Roger,

I'd expect that the farther one looks from a big event, the less distant triggering will appear. The surface waves dominate the long period motions and the energy budget, and they have no shadow zone nor secondary peaks far from the source.

There can be a noticeable amplification of shaking from Moho reflections, but that is far closer, less than a few 100 km.

Canie, the seiches, from what we know, do not arise from distant focusing.

John