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Tsunami Preparedness Information

What is a Tsunami?
A tsunami (pronounced "soo-nahm'ee") is a series of waves generated by an undersea disturbance such as an earthquake. From the area of the disturbance, the waves will travel outward in all directions, much like the ripples caused by throwing a rock into a pond. The time between wave crests may be from 5 to 90 minutes, and the wave speed in the open ocean may be more than 450 miles per hour. Tsunamis have reached heights of more than 100 feet. As the waves approach shallow coastal waters, they appear normal and the speed decreases. Then as the tsunami nears the coastline, it may grow to great height and smash into the shore, causing great destruction and loss of life.

  1. Tsunamis are caused by an underwater disturbance - usually an undersea earthquake. Landslides, volcanic eruptions, and even meteorites can also generate a tsunami.
  2. Tsunamis can originate hundreds or even thousands of miles away from coastal areas. Local geography may intensify the effect of a tsunami. Areas at greatest risk are less than 50 feet above sea level and within one mile of the shoreline.
  3. People who are near the seashore during a strong earthquake should listen to a radio for a tsunami warning and be ready to evacuate at once to higher ground.
  4. Rapid changes in the water level are an indication of an approaching tsunami.
  5. Tsunamis arrive as a series of successive "crests" (high water levels) and "troughs" (low water levels). These successive crests and troughs can occur anywhere from 5 to 90 minutes apart. They usually occur 10 to 45 minutes apart.

What is the Tsunami Risk to the Gulf of Mexico?
Tsunamis have occurred in the Gulf of Mexico. In 1991, a magnitude 7.6 earthquake in Costa Rica produced a six foot high tsunami that flooded nearly 1,000 feet inland on the Caribbean side of the country. The Caribbean also has a number of active submarine volcanoes and fault systems that are capable of producing earthquakes large enough to generate tsunamis. The Gulf is also at risk from very large tsunamis that originate in the Atlantic Ocean, like the one produced by the 1755 Lisbon earthquake. There are no authoritative estimates of the extent of the risk that these hazards may pose to states with coastlines on the Gulf of Mexico.

Warning of a Tsunami Threat
There is presently no dedicated tsunami warning system for the Gulf of Mexico, but government agencies can be expected to disseminate warnings of potential threats caused by seismic and volcanic events through the Emergency Alert System and the news media. The U.S. Pacific tsunami detection and warning system is in the process of being expanded to include the Caribbean, the Gulf of Mexico, and areas of the Atlantic that could affect the U.S. coast. The National Oceanic and Atmospheric Administration (NOAA) will deploy 32 new tsunami detection buoys for a more extensive tsunami warning system by mid-2007.

Tsunami Preparedness & Response Actions
If you live, work, or are visiting in a coastal area and are advised that a threat of tsunami exists:

If you are advised by local officials to evacuate: