I see you that you were able to spell it better than I did.

Tsunamis require a lot of motion of the seafloor. So an M9 quake under the ocean will do it every time, but an M7 will not, and an M8 might or might not be deadly. However, some quakes trigger underwater landslides, which occasionally are deadly themselves when they are large enough.

So it is a judgement call when to declare a warning. Until the waves are measured, it is hard to know for sure how big they will be, and then it is too late for the closest shores.

It is true that thrust quakes generate bigger waves than strike-slip events, but this is less important than the magnitude of the earthquake and whether slides are triggered.