Tsunami

Tsunami (pronounced soona-mee), sometimes called a tidal wave, is actually a series of enormous waves created by an underwater disturbance or earthquake. Tsunamis can move hundreds of miles per hour in the open ocean and smash into land with waves more than 100 feet high. In this century, more than 200 tsunamis have been recorded in the Pacific Ocean alone.

All tsunamis are potentially dangerous, even though they may not damage every coastline they strike - some waves in the series are less hazardous than others. Tsunamis can strike anywhere along most of the U.S. coastline. The most destructive tsunamis have occurred along the coasts of California, Oregon, Washington, Alaska and Hawaii.

How to prepare for a tsunami

1. Heed tsunami warnings ‑ they mean a tsunami exists. Listen to radio or television for information and follow the instructions of your local authorities.

2. Advance warning of tsunamis sometimes comes in the form of a noticeable rise or fall in the normal depth of coastal water. This is nature's tsunami warning and should be heeded.

3. If you feel an earthquake in a Pacific Coast area, turn on your battery‑powered radio to learn if there is a tsunami warning.

4. A small tsunami at one beach can be a giant wave a few miles away. Do not let the modest size of one wave allow you to forget how dangerous tsunamis are. The next wave may be bigger.

5. Prepare ahead for possible evacuation. See the Evacuation and Emergency Planning and Checklists page for information.

What to do if a tsunami threatens your area

1. If you are advised to evacuate, do so immediately.

2. Stay away from the area until local authorities say it is safe. Do not be fooled into thinking that the danger is over when a single wave has come and gone - a tsunami is not a single wave but a series of waves.

3. Do not go to the shoreline to watch for a tsunami. When you can see the wave, it is too late to escape it.