Tsunami Preparedness Week
How a Tsunami Works
Most tsunamis are
caused by undersea
earthquakes, as
shown here, but
they can also be
caused by landslides,
volcanic activity, and
even meteorites.
1
An underwater earthquake occurs when a plate shifts abruptly
and pushes water upward with tremendous force.
2
Low and fast waves are generated in all directions across the
ocean, some speeding as fast as 600 mph.
3
As waves enter shallower water, they are compressed,
their speed slows, and they build in height.
4
The wave height increases, and associated currents
intensify, becoming a threat to life and property.
http://www.tsunami.noaa.gov/
Tsunami Preparedness Week
Know Your Risk
Tsunami risk is greatest
around the Pacific Basin.
Volcanic arcs (orange) and
oceanic trenches (blue)
make up the Pacific Ocean
basin’s Ring of Fire, an area
prone to earthquakes that
may trigger tsunamis.
Credit: U.S. Geological Survey
http://1.usa.gov/1gxKbFm
Tsunami Preparedness Week
Know Your Risk
Ask your local or state emergency management office
or your local National Weather Service office to learn
about your community’s tsunami risk.
Examples of tsunami evacuation maps
Crescent City, California
Vega Baja, Puerto Rico
http://www.tsunami.noaa.gov/
Tsunami Preparedness Week
Tsunami Messages
Warning:
Warning: A tsunami with potential for
widespread inundation is imminent,
expected, or occurring. Dangerous coastal
flooding and powerful currents are
possible and may continue for several
hours after initial arrival.
Advisory:
Advisory: A tsunami with potential for
strong currents or waves dangerous to
those in or very near the water is
imminent, expected, or occurring.
Significant inundation is not expected.
NOAA Weather Radio All Hazards
http://www.nws.noaa.gov/nwr/
Watch:
Watch: A potentially dangerous distant
seismic event has occurred that may later
impact the watch area with a tsunami.
Information
InformationStatement:
Statement: An earthquake
has occurred, or a tsunami warning,
watch, or advisory has been issued for
another section of the ocean. In most
cases, an information statement indicates
there is no threat of a destructive tsunami
in your area.
Adapted from: http://ntwc.arh.noaa.gov/
http://www.tsunami.gov/
Tsunami Preparedness Week
1964 Great Alaska Earthquake and Tsunamis
Credit: NOAA
http://1.usa.gov/1gCxptu
Tsunami Preparedness Week
Tsunami Safety
⁻
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Danger!
Run for high ground
Follow emergency instructions
WARNING
ADVISORY
⁻
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Possible dangerous currents
Move off the beach & stay out of the water
WATCH
⁻
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Potential danger
Stay tuned for more information
INFORMATION STATEMENT
Relax
No local danger
A distant ocean basin may be in danger
http://1.usa.gov/1hwqfVD
Tsunami Preparedness Week