Tsunami exercise "LANTEX 10" commenced at midnight GMT today, with the first message sent by the West Coast/Alaska Tsunami Warning Centre. This is a scripted exercise to test tsunami response plans. LANTEX 10, simulates a magnitude 7.5 earthquake off the New England coast. Detail of the exercise, including the timeline of what is scheduled to happen when is available in the LANTEX10 Handbook Version 3.0.
There is also the corresponding Pacific exercise PACIFEX 10, simulating a magnitude 9.0 earthquake south of the Alaska Peninsula. Details are in the PACIFEX10 Handbook Version 3.0. In addition Alaska and California are conducting tests of their Emergency Alert Systems, including on TV and radio the same day.
It should be noted for those used to more free flowing exercises, as used by the UK and Australia, the US exercises tend to be more tightly scripted.
ps: Also note, as it says in all messages issued: THIS IS ONLY AN EXERCISE.