In other words, there almost always is a tsunami in a 8+ quake in the ocean. It's just that, as the article says, such a tsunami needn't be "devastating."
It all depends on whether or not the movement is horizontal or vertical.
Again, here's that article. Check it out. It explains everything. No need to wait for the research (unless you are of a scientific bent and would like to go into it in depth). Cheers!
Awesome. Thanks so much. It’s amazing that the vertical movement so so little that the tsunami was unnoticeable. Lucky break for all.