I was astonished today to read in some news source that 90% of the tsunamis are in the Pacific! No wonder they were less inclined to think one was forming.
Some tsunamis are very local -- Japan, Alaska, Islands like Hawaii, etc.
The volcano Krakatoa erupted [blew up is the correct word] in 1883. The tsunami generated reached San Francisco -- although it was only 0.1 meters high.
But when Krakatoa went off in the same general area, the explosion was so loud that the Island of Diego Garcia, over 2000 miles away, the people thought a ship was firing its cannons because it was in distress. Sort of like something happening in Houston, Texas or New Orleans, LA and being heard in Los Angeles -- though the open sea conducts sound much better than land masses such as the Rocky Mountains.