Here's something extra from the Mexico earthquake thing. These are my picks of the smooth arcs of the Pacific Rim. These arcs represent the maximum fractal dimension, which is the max size that a fault retains self-similarity. I'm saying that sooner or later these things rip into a huge M9ish. The tiny arc by Japan is that last M9. An M10 would be 10 times longer and we can't fit that! These arcs that are a few times longer than Japan only give an M9.3 or something.
Ground motion (PGV) probably saturates on firm ground at M7. A California soil basin - M8. Mexico City - M9. Tsunamis don't saturate.