4. Size of Tsunami
• Tsunamis have an extremely long wavelength (wavelength is the distance
between the crest (top) of one wave and the crest of the next wave) -- up to
several hundred miles long. The period (the time between two successive waves)
is also very long -- about an hour in deep water.
• In the deep sea, a tsunami's height can be only about 1 m (3 feet) tall.
Tsunamis are often barely visible when they are in the deep sea. This makes
tsunami detection in the deep sea very difficult.
• A tsunami can travel at well over 970 kph (600 mph) in the open ocean - as
fast as a jet flies. It can take only a few hours for a tsunami to travel across
an entire ocean. A regular wave (generated by the wind) travels at up to about
5. Facts About Tsunamis
• Tsunami is should not be known as tidal waves. Tsunamis are sometimes incorrectly
called "tidal waves" -- tsunamis are not caused by the tides (tides are caused by the
gravitational force of the moon on the sea). Regular waves are caused by the wind.
• If the first part of a tsunami to reach land is a trough—called a drawback—rather
than a wave crest, the water along the shoreline recedes dramatically, exposing
normally submerged areas.
• Most tsunamis, about 80 percent, happen within the Pacific Ocean’s “Ring of Fire,” a
geologically active area where tectonic shifts make volcanoes and earthquakes
• A tsunami may be less than a foot (30 centimeters) in height on the surface of the
open ocean, which is why they are not noticed by sailors. But the powerful shock wave
of energy travels rapidly through the ocean as fast as a commercial jet. Once a
tsunami reaches shallow water near the coast, it is slowed down. The top of the wave
moves faster than the bottom, causing the sea to rise dramatically.
6. • Geological features such as reefs, bays, river entrances, and
undersea formations may dissipate the energy of a tsunami. In
some places a tsunami may cause the sea to rise vertically only a
few inches or feet
• Flooding can extend inland by a thousand feet (300 meters) or
more. The enormous energy of a tsunami can lift giant boulders,
flip vehicles, and demolish houses. Knowledge of the history of
tsunamis in your area is a good indicator of what is likely to
happen in a future tsunami event.
• The 2004 Indian Ocean tsunami could rank as the most
devastating on record. More than 200,000 people lost their lives,
many of them washed out to sea.
7. Warning signs
An earthquake is a natural tsunami warning. If you feel a strong quake do not stay in
a place where you are exposed to a tsunami. If you hear of an earthquake be aware of the
possibility of a tsunami and listen to the radio or television for additional
information. Remember that an earthquake can trigger killer waves thousands of miles
across the ocean many hours after the event generated a tsunami.
Witnesses have reported that an approaching tsunami is sometimes preceded by a
noticeable fall or rise in the water level. If you see the ocean receding unusually rapidly
or far it's a good sign that a big wave is on its way. Go to high ground immediately.
Many people were killed by the Indian Ocean tsunami because they went down to the beach
to view the retreating ocean exposing the seafloor. Experts believe that a receding ocean
may give people as much as five minutes' warning to evacuate the area.
Remember that a tsunami is a series of waves and that the first wave may not be the most
dangerous. The danger from a tsunami can last for several hours after the arrival of the
first wave. A tsunami wave train may come as a series of surges that are five minutes to
an hour apart. The cycle may be marked by a repeated retreat and advance of the ocean.
8. Survivors of the Indian Ocean tsunami reported that the sea surged out as fast
and as powerfully as it came ashore. Many people were seen being swept out to
sea when the ocean retreated.
A tsunami surge may be small at one point of the shore and large at another
point a short distance away. Do not assume that because there is minimal
sign of a tsunami in one place it will be like that everywhere else.
Tsunamis can travel up rivers and streams that lead to the ocean. Stay away
from rivers and streams that lead to the ocean as you would stay away from
the beach and ocean if there is a tsunami.
It's always a good idea to keep a store of emergency supplies that include
sufficient medications, water, and other essentials sufficient for at least 72
hours. Tsunami, earthquake, hurricane—an emergency can develop with little
or no warning.
9. Plan for a Tsunami
• Develop a Family Disaster Plan
• Learn about tsunami risk in your community
• If you are visiting an area at risk from tsunamis, check with the
hotel, motel, or campground operators for tsunami evacuation
• Plan an evacuation route from your home, school, workplace, or any
other place you'll be where tsunamis present a risk.
• Practice your evacuation route
• Use a NOAA Weather Radio with a tone-alert feature to keep you
informed of local watches and warnings.
• Discuss tsunami with your family
• Assemble a Disaster Supplies Kit
10. How to Protect Your
• Avoid building or living in buildings within several hundred feet of the
coastline. These areas are more likely to experience damage from tsunamis,
strong winds, or coastal storms.
Make a list of items to bring inside in the event of a tsunami. A list will
help you remember anything that can be swept away by tsunami waters.
• Elevate coastal homes. Most tsunami waves are less than 10 feet. Elevating
your house will help reduce damage to your property from most tsunamis.
• Follow flood preparedness precautions. Tsunamis are large amounts of
water that crash onto the coastline, creating floods.
• Have an engineer check your home and advise about ways to make it more
resistant to tsunami water. There may be ways to divert waves away from
your property. Improperly built walls could make your situation worse.
Consult with a professional for advice.
11. What to Do After a Tsunami
• Continue listening to a NOAA Weather Radio, Coast Guard
emergency frequency station, or other reliable source for
• Help injured or trapped persons
• Use the telephone only for emergency calls
• Stay out of the building if waters remain around it
• Examine walls, floors, doors, staircases, and windows to
make sure that the building is not in danger of collapsing.
12. • Inspect foundations for cracks or other damage
• Look for fire hazards.
• Check for gas leaks
• Look for electrical system damage.
• Check food supplies. Any food that has come in contact
with flood waters may be contaminated and should be
13. Did you know?
• A Tsunami wave can reach over 100 ft. or higher onto
• Tsunami waves can be up to 60 mph.
• Tsunami waves are powerful enough to lift giant boulders,
lift vehicles, and demolish houses.
• These waves can cross an entire city without losing any
14. • Hawaii is the number one STATE at risk for a Tsunami
and they average about 1 per year.
• Many say Tsunamis sound like a freight train.
• Right before a Tsunami strikes the ocean can drain away.
• Although Tsunamis are dangerous, Palm trees can survive