The National Oceanic and Atmospheric Administration (NOAA) defines a tsunami as a series of ocean waves caused by any rapid large-scale disturbance of the seawater. Earthquakes generate most tsunamis, but volcanic eruptions, landslides, undersea slumps or meteor impacts may also cause them.
The following resources from U.S. Government agencies and nonprofit organizations can help you deal with a tsunami.
Safety resources and information on how the Tsunami Warning System works
(National Oceanic and Atmospheric Administration)
Information on what to do after a tsunami
Information on the health effects of tsunamis as well as tips on food & water safety
(Centers for Disease Control)
Advice on what to do before, during and after a tsunami
(American Red Cross)