What Is A Tsunami?
Tsunami (soo-NAH-mee): a Japanese word that means harbor wave; a sea
wave of local or distant origin that results from large-scale seafloor
displacements associated with large earthquakes, major submarine slides,
or exploding volcanic islands. Typically generated by seismic or volcanic
activity or by underwater landslides, a tsunami consists of a series of
high-energy waves that radiate outward like pond ripples from the area in
which the generating event occurred.
Not all earthquakes produce tsunamis. To generate a tsunami, an earthquake
must occur underneath or near the ocean, be very large (approximately Richter
magnitude 7 or greater), and create vertical movement of the sea floor. However,
recent studies regarding the potential for a great Cascadia Subduction zone
earthquake off the Washington, Oregon, and Northern California coastlines
indicate the local tsunami waves may reach nearby coastal communities within
minutes of the earthquake thereby giving little or no time to issue
How will I know if a Tsunami is coming?
The West Coast/Alaska Tsunami Warning Center (WC/ATWC) is responsible for
tsunami warnings for California, Oregon, Washington, British Columbia and
The Pacific Tsunami Warning Center (PTWC) provides warnings to
international authorities, Hawaii, and U.S. Territories within the Pacific
The WC/ATWC and PTWC may issue the following bulletins:
- Information: A message with information about an earthquake
that is not expected to generate a tsunami.
- Advisory: An earthquake has occurred in the Pacific Basin, which
might generate a tsunami.
- Watch: A tsunami was or may have been generated, but is at
least two hours travel time to the area in Watch status.
- Warning: A tsunami was, or may have been generated, which could cause
damage; therefore, people in the warned area are strongly advised to evacuate.
- A warning siren may sound.
- Seawater may recede quickly.
- The ground may shake, indicating an earthquake has occurred.
- Your NOAA Tone Alert radio issues a warning that a tsunami may be headed to your area.
- Sign up for free
Email and Text Mesage Tsunami Alerts from the Pacific Tsunami Warning Center
Tsunami Evacuation Maps
Additional information on evacation routes for Hawai'i can be found at the following link; Hawai'i Evacuation routes.