Way under 1 in 10 tsunamis
I can come up with 10 Pacific ocean earthquake related tsunamis off the top of my head. We have many, many known tsunamis not only from historical records, but from finding deposits in coastal areas. If 10% are due to impacts there ought to be a lot of seemingly misplaced tsunamis nowhere near known fault zones. To me knowledge, geologists haven't found any such thing.
We do know of a couple of impact related tsunamis, most notably deposits around the Gulf of Mexico from the KT impact. But mostly, tsunamis seem very well accounted for by earthquakes and sometimes landslides (e.g., sector collapse of mid-ocean volcanic islands).
1 in 10 is too high by a LOT.