Whenever we go to the coast, we always see "tsunami evacuation route" signs and are amused since it seems so foreign to us having not grown up in this area. Some locals in small towns along the coast have removed the signs so that tourists aren't scared away. But tsunamis really are very dangerous and apparently the West Coast is totally unprepared for such an event. Apparently there's a series of 39 buoys all along the coast from Alaska to South America that are supposed to detect tsunami waves and alert areas that will be affected by them. However as many as a third of them are down for maintenance issues at various times.

The last earthquake and tsunami from the Cascadia fault occurred 300 years ago. The last tsunami to hit the northwest coast was in 1964 when an Alaska earthquake caused a tsunami that damaged Cannon Beach, OR. Here's an excerpt from a Seattle Times article that explains what parts of the northwest coast are considering in order to be more prepared for tsunamis:

The Oregon town of Cannon Beach is considering construction of an earthquake- and tsunami-resistant building that could serve both as a city hall and a refuge. On Washington's Long Beach Peninsula, where there's very little high ground, leaders are mulling the idea of building berms where people could gather to escape a tsunami surge.

We live near Puget Sound, which isn't that close to the Pacific Ocean, so tsunamis aren't as big of a threat to us, but are still possible.