The lateral beams expand in width with distance and the length of fault rupture in the Chile quake was exceedingly long.
You have local amplification effects in places like Crescent City from the topography of the bottom as well, of course.
My main point is people shouldn't be making judgements of the size of any possible tsunami from tide stations on Hokkaido, which are oriented along the fault itself in the same way as Bangladesh (which saw basically no tsunami at all) was to the 2004 Sumatran quake.
OK, well said then. I agree that tide stations are for scientists to determine the probable effects, not for casual observers and so we shouldn't be trying to get too much information out of that data without being properly trained.