Tsunamis

A tsunami (pronounced “soo-nah-mee”) is a series of ocean waves caused by any large, abrupt disturbance of the sea-surface. Earthquakes cause most tsunamis, but a tsunami can also be generated by landslides, volcanic activity, or rarely by meteor impact. If the disturbance is close to the coastline, a local tsunami can cause death and destruction among coastal communities within minutes. A very large disturbance, such as the magnitude 9.0 earthquake off the Sumatra coast in 2004, can generate waves that cause local devastation and destruction thousands of miles away. To learn more about tsunamis, read NOAA’s Tsunami Story.

A NOAA DART II tsunami buoy Learn more...

In the deep ocean, the tsunami wave may only be a few centimeters high. However, tsunami waves, because of their long wavelengths, lose little energy as they travel. This means that while the tsunami wave may come gently ashore, depending on the energy, landforms, direction of travel, tides and other factors the wave may come ashore as a deadly, fast moving wall of turbulent water several meters high. In deep water, the waves may reach speeds exceeding 700 kilometers per hour.

While the frequency of damaging tsunamis in the United States coastal areas is low compared to many other natural hazards, the impacts can be extremely high. Tsunamis cannot be prevented but the impact of a tsunami can be mitigated through community preparedness, timely warnings, and effective response. Developing tsunami-resilient communities depends on enhanced Federal, State and local capabilities in each of the following seven areas:

• Determining the Threat


• Preparedness


• Timely and Effective Warnings


• Mitigation


• Public Outreach and Communication


• Research


• International Coordination

NOAA has primary responsibility for providing tsunami warnings to the Nation, and a leadership role in tsunami observations and research. For more information about tsunamis and building tsunami resilient communities, visit NOAA’s Tsunami Website.