Facts: Tsunamis normally have the appearance of a fast-rising and fast-receding flood. They can be similar to a tide cycle occurring over 10 to 60 minutes instead of 12 hours. Occasionally, tsunamis can form walls of water, known as tsunami bores, when the waves are high enough and the shoreline configuration is appropriate.
Fiction: A tsunami is a single wave.
Facts: A tsunami is a series of waves. Often the initial wave is not the largest. The largest wave may occur several hours after the initial activity starts at a coastal location. There may also be more than one series of tsunami waves if a very large earthquake triggers local landslides. In 1964, the town of Seward, Alaska, was devastated first by local tsunamis caused by submarine landslides resulting from the earthquake and then by the earthquakes main tsunami. The local tsunamis began even as people were still experiencing the shaking. The main tsunami, triggered at the site of the earthquake, did not arrive for several hours.
Fiction: Boats should move to the protection of a bay or harbor during a tsunami.
Facts: Tsunamis are often most destructive in bays and harbors, not just because of the waves but because of the violent currents they generate in local waterways. Tsunamis are least destructive in deep, open ocean waters.
Source: Talking About Disaster: Guide for Standard Messages. Produced by the National Disaster Education Coalition, Washington, D.C., 2004.