emergency preparedness, disaster preparedness, preparedness, tsunami

Tsunamis

Tsunami is sometimes mistaken for a tidal wave, but it is a series of enormous waves created by an underwater disturbance such as an earthquake. They can also be generated by landslides, volcanic eruptions and even meteorites. But meteorites are usually too small to generate a tsunami. A tsunami can move hundreds of miles per hour in the open ocean and smash into land with waves as high as 100 feet or more, although most waves are less than 18 feet high. The effects of a tsunami are always devastating due to the immense volumes of water and energy involved. 

In deep water, the tsunami wave is not noticeable. Once the wave approaches the shore it builds in height. A tsunami can strike anywhere along the U.S. coastline. The most destructive tsunamis have occurred along the coasts of California, Oregon, Washington, Alaska and Hawaii.

If a major earthquake or landslide occurs close to shore, the first wave in a series could reach the beach in a few minutes, even before a warning is issued. Drowning is the most common cause of death associated with a tsunami. Other hazards include flooding, contamination of drinking water and fires from gas lines or ruptured tanks.

BEFORE:

1. Know the terms used to describe a tsunami threat:

  • Tsunami Advisory - An earthquake has occurred in the ocean which might generate a tsunami.
  • Tsunami Watch - A tsunami was or may have been generated, but is at least two hours travel time to the area in Watch status.
  • Tsunami Warning - A tsunami was or may have been generated, which could cause damage; therefore, people in the warned area are strongly advised to evacuate.

2. Know and practice your emergency plan.

3. Have your 3-day emergency kit readily available as well as a small emergency kit in your vehicle. Click here for ideas on how to put one together yourself.

4. If you feel an earthquake in a coastal area, listen to radio or television stations for current information.

5. If the first part of a tsunami to reach land is a trough (draw back) rather than a crest of the wave, the water along the shoreline may recede dramatically, exposing areas that are normally always submerged. This can serve as an advance warning of the approaching tsunami which will rush in faster than it is possible to run. If a person is in a coastal area where the sea suddenly draws back (many survivors report an accompanying sucking sound), their only real chance of survival is to run for high ground or seek the high floors of high rise buildings.

6. Know that a small tsunami at one beach can be a giant wave a few miles away.

7. A tsunami may generate more than one wave. Do not let the modest size of one wave allow you to forget how dangerous a tsunami is. The next wave may be bigger.

DURING:

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

2. Stay away from the area until local authorities say it is safe to return. Do not be fooled into thinking the danger is over after a single wave - a tsunami is not a single wave but a series of waves than can vary in size.

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

AFTER:

1. Avoid flooded and damaged areas until officials say it is safe to return.

2. Stay away from debris in the water, it may pose a safety hazard to boats and people.