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Twenty-four tsunamis have caused damage in the United States
territories during the last 204 years. Just since
1946, six tsunamis
have killed more than 350 people and caused a half billion
of property damage in Hawaii, Alaska, and the West Coast. As a tsunami
nears the coastline, it may rise to several feet or, in rare cases,
of feet, and can cause great loss of life and property damage when it
ashore. Tsunamis can travel upstream in coastal estuaries and
with damaging waves extending farther inland than the immediate coast.
tsunami can occur during any season of the year and at any time, day or
What Are Tsunamis, and What Causes Them?
Tsunamis are ocean waves produced by earthquakes or underwater
The word is Japanese and means "harbor wave," because of the
effects these waves have had on low-lying Japanese coastal communities.
Tsunamis are often incorrectly referred to as tidal waves, but a
is actually a series of waves that can travel at speeds averaging 450
(and up to 600) miles per hour in the open ocean.
In the open ocean,
tsunamis would not be felt by ships because the wavelength would be
of miles long, with an amplitude of only a few feet. This would also
them unnoticeable from the air. As the waves approach the
speed decreases and their amplitude increases. Unusual wave
have been known to be over 100 feet high. However, waves
that are 10
to 20 feet high can be very destructive and cause many deaths or
Tsunamis are most often generated by
of the ocean floor. Landslides, volcanic eruptions, and even
can also generate a tsunami. If a major earthquake is felt, a tsunami
reach the beach in a few minutes, even before a warning is issued.
at greatest risk are less than 25 feet above sea level and within one
of the shoreline. Most deaths caused by a tsunami are because
risks include flooding, water
fires from ruptured
tanks or gas lines, and the loss of vital community infrastructure
fire, and medical facilities).
From an initial tsunami generating source area, waves
in all directions much like the ripples caused by throwing a rock into
a pond. As these waves approach coastal areas, the time
wave crests varies from 5 to 90 minutes. The first wave is usually not
the largest in the series of waves, nor is it the most significant.
one coastal community may experience no damaging waves while another,
that far away, may experience destructive deadly waves. Depending on a
number of factors, some low-lying areas could experience severe inland
inundation of water and debris of more than 1,000 feet.
Learn whether tsunamis have occurred in your area by
local emergency management office, National Weather Service office, or
Red Cross chapter. If you are in a tsunami risk
area, learn how
to protect yourself, your family, and your property.
Warning Center (WC/ATWC) is responsible for tsunami
California, Oregon, Washington, British Columbia, and Alaska.
The Pacific Tsunami Warning Center (PTWC)
is responsible for
providing warnings to international authorities, Hawaii, and U. S.
within the Pacific basin. The two Tsunami Warning Centers coordinate
information being disseminated.
All tsunamis are potentially dangerous, even
though they may not
damage every coastline they strike. Damaging tsunamis are very rare.
coastlines are vulnerable, but tsunamis are infrequent. Understand the
hazard and learn how to protect yourself, but don't let the threat of
ruin your enjoyment of the beach.
The WC/ATWC and PTWC may issue the following bulletins:
Be familiar with the tsunami warning signs. A strong
lasting 20 seconds or more near the coast may generate a tsunami. A
rapid rise or fall in coastal waters is also a sign that a tsunami is
- WARNING: A tsunami was or may have
generated, which could cause
damage; therefore, people in the warned area are strongly advised to
- WATCH: A tsunami was or may have been
generated, but is at least
two hours travel time to the area in watch status. Local officials
prepare for possible evacuation if their area is upgraded to a warning.
- ADVISORY: An earthquake has occurred
Pacific basin, which
might generate a tsunami. WC/ATWC and PTWC will issue hourly bulletins
advising of the situation.
- INFORMATION: A message with
an earthquake that
is not expected to generate a tsunami. Usually only one bulletin is
Tsunamis most frequently come onshore as a rapidly
surge of water choked with debris. They are not V-shaped or rolling
and are not "surfable."
Tsunamis may be locally generated or from a distant
1992, the Cape Mendocino, California, earthquake produced a tsunami
reached Eureka in about 20 minutes, and Crescent City in 50 minutes.
this tsunami had a wave height of about one foot and was not
it illustrates how quickly a wave can arrive at nearby coastal
and how long the danger can last.
In 1957, a distant-source tsunami generated
by an earthquake in
the Aleutian Islands in Alaska struck Hawaii, 2,100 miles away. Hawaii
experienced $5 million in damages from that tsunami.
Plan for a Tsunami
Develop a Family Disaster Plan. Please see the
Disaster Plan" section
for general family
planning information. Tsunami-specific planning should include the
- Learn about tsunami risk in your community.
Contact your local emergency
management office or American
Red Cross chapter. Find out if your home, school, workplace
frequently visited locations are in tsunami hazard areas. Know the
of your street above sea level and the distance of your street from the
coast or other high-risk waters. Evacuation orders may be based on
- If you are visiting an area at risk from
with the hotel,
motel, or campground operators for tsunami evacuation information and
you would be warned. It is important to know designated
before a warning is issued.
If you are at risk from tsunamis, do the following:
- Plan an evacuation route from your home, school,
workplace, or any other
place you'll be where tsunamis present a risk. If possible,
area 100 feet above sea level or go up to two miles inland, away from
coastline. If you can't get this high or far, go as high as you can.
foot inland or upwards may make a difference. You should be able to
your safe location on foot within 15 minutes. After a disaster, roads
become impassable or blocked. Be prepared to evacuate by foot if
Footpaths normally lead uphill and inland, while many roads parallel
Follow posted tsunami evacuation routes; these will lead to safety.
emergency management officials can help advise you as to the best route
to safety and likely shelter locations.
- Practice your evacuation route.
save your life.
Be able to follow your escape route at night and during inclement
Practicing your plan makes the appropriate response more of a reaction,
requiring less thinking during an actual emergency situation.
- Use a NOAA Weather Radio with a tone-alert
feature to keep
of local watches and warnings. The tone alert feature will
of potential danger even if you are not currently listening to local
or television stations.
- Talk to your insurance agent.
policies do not cover
flooding from a tsunami. Ask about the National Flood Insurance Program.
- Discuss tsunami with your family.
should know what to do
in case all family members are not together. Discussing tsunamis ahead
of time will help reduce fear and anxiety, and let everyone know how to
respond. Review flood safety and preparedness measures with your family.
Assemble a Disaster
Please see the section "Disaster
for general supplies kit information. Tsunami-specific supplies should
include the following:
- Evacuation Supplies Kit in an easy-to-carry
- Disaster Suplies Kit basics.
How to Protect Your Property
- Avoid building or living in buildings within
hundred feet of
the coastline. These areas are more likely to experience
tsunamis, strong winds, or coastal storms.
- Make a list of items to bring inside in the
event of a
A list will help you remember anything that can be swept away by
- Elevate coastal homes. Most tsunami
less than 10 feet.
Elevating your house will help reduce damage to your property from most
- Follow flood
Tsunamis are large amounts of water that crash onto the coastline,
- 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
from your property. Improperly built walls could make your situation
Consult with a professional for advice.
Media and Community Education Ideas
- If your community is at risk, build and
locations of tsunami
evacuation routes. Post signs directing people to higher
from the coast.
- Review land use in tsunami hazard areas so
such as hospitals and police stations; or high occupancy buildings,
as auditoriums or schools; or petroleum-storage tank farms are located
where there is a tsunami hazard. Tsunami damage can be minimized
land use planning, preparation, and evacuation.
- Publish a special section in your local
on tsunamis. Localize the information by printing the phone
of local emergency services offices, the American Red Cross chapter,
- Periodically inform your community of local
- Work with local emergency services and American
to prepare special reports for people with mobility impairments on what
to do if an evacuation is ordered, and develop plans to assist them
evacuation if necessary.
- Interview local officials and insurance
types of insurance to cover a flood-related loss. Include information
the economic effects of disaster.
What to Do if You Feel a Strong Coastal Earthquake
If you feel an earthquake that lasts 20 seconds or longer when
you are on the coast:
- Drop, cover, and hold on. You should
protect yourself from
- When the shaking stops, gather your family
Leave everything else behind. A tsunami may be coming within
quickly to higher ground away from the coast.
- Be careful to avoid downed power lines and stay
and bridges from which heavy objects might fall during an
What to Do When a Tsunami WATCH is Issued
- Listen to a NOAA Weather Radio, Coast Guard
or other reliable source for updated emergency information.
energy of a tsunami is transferred through open water, it is not
Seismic action may be the only advance warning before the tsunami
- Check your Disaster Supplies Kit. Some
may need to be replaced
- Locate family members and review evacuation
Make sure everyone
knows there is a potential threat and the best way to safer ground.
- If you have special evacuation needs (small
or persons with disabilities) consider early evacuation.
may take longer, allow extra time.
- If time permits, secure unanchored objects
home or business.
Tsunami waves can sweep away loose objects. Securing these items or
them inside will reduce potential loss or damage.
- Be ready to evacuate. Being prepared
you to move more
quickly if a tsunami warning is issued.
What to Do When a Tsunami WARNING is Issued
Return home only after local officials tell you it is safe.
is a series of waves that may continue for hours. Do not
after one wave the danger is over. The next wave may be
the first one.
- Listen to a NOAA Weather Radio, Coast Guard
or other reliable source for updated emergency information.
will issue a warning only if they believe there is a real threat from
- Follow instructions issued by local authorities.
routes may be different from the one you use, or you may be advised to
- If you are in a tsunami risk area, do the following:
- If you hear an official tsunami warning or
of a tsunami,
evacuate at once. A tsunami warning is issued when
certain that a tsunami threat exists, and there may be little time to
- Take your Disaster Supplies Kit.
supplies will make you more
comfortable during the evacuation.
- Get to higher ground as far inland as possible.
reliably predict either the height or local effects of tsunamis.
a tsunami from the beach or cliffs could put you in grave danger. If
can see the wave, you are too close to escape it.
What to Do After a Tsunami
- Continue listening to a NOAA
Weather Radio, Coast Guard emergency frequency station, or
source for emergency information. The tsunami may have
bridges, or other places that may be unsafe.
- Help injured or trapped persons. Give first aid
Call for help. Do not move seriously injured persons unless they are in
immediate danger of further injury.
- Help a neighbor who may require special
people, and people with disabilities. Elderly people and
disabilities may require additional assistance. People who care for
or who have large families may need additional assistance in emergency
- Use the telephone only for emergency calls.
Telephone lines are
frequently overwhelmed in disaster situations. They need to be clear
emergency calls to get through.
- Stay out of the building if waters remain around
like flood waters, can undermine foundations, causing buildings to
floors to crack, or walls to collapse.
- When re-entering buildings or homes, use extreme
flood waters may have damaged buildings where you least expect it.
watch every step you take.
- Wear sturdy shoes. The most common
following a disaster is
- Use battery-powered lanterns or flashlights
Battery-powered lighting is the safest and easiest, preventing fire
for the user, occupants, and building.
- Examine walls, floors, doors, staircases, and
make sure that
the building is not in danger of collapsing.
- Inspect foundations for cracks or other damage.
Cracks and damage
to a foundation can render a building uninhabitable.
- Look for fire hazards. There may be
leaking gas lines,
flooded electrical circuits, or submerged furnaces or electrical
Flammable or explosive materials may come from upstream. Fire is the
frequent hazard following floods.
- Check for gas leaks. If you smell
gas or hear
a blowing or hissing
noise, open a window and quickly leave the building. Turn off the gas
the outside main valve if you can, and call the gas company from a
home. If you turn off the gas for any reason, it must be turned back on
by a professional.
- Look for electrical system damage.
If you see
sparks or broken or
frayed wires, or if you smell burning insulation, turn off the
at the main fuse box or circuit breaker. If you have to step in water
get to the fuse box or circuit breaker, call an electrician first for
Electrical equipment should be checked and dried before being returned
- Check for sewage and water line damage.
suspect sewage lines
are damaged, avoid using the toilets and call a plumber. If water pipes
are damaged, contact the water company and avoid using water from the
You can obtain safe water from undamaged water heaters or by melting
- Use tap water if local health officials advise
- Watch out for animals, especially poisonous
may have come
into buildings with the water. Use a stick to poke through debris.
Tsunami flood waters flush snakes and animals out of their homes.
- Watch for loose plaster, drywall, and ceilings
- Take pictures of the damage, both of the
for insurance claims.
- Open the windows and doors to help dry the
- Shovel mud while it is still moist to give walls
floors an opportunity
- Check food supplies. Any food that has
contact with flood
waters may be contaminated and should be thrown out.
Produced by the National
Disaster Education Coalition: American
Red Cross, FEMA,
IAEM, IBHS, NFPA, NWS, USDA/CSREES,
and USGS. HTML
formating By the
From: Talking About Disaster: Guide for Standard
by the National Disaster Education Coalition, Washington, D.C., 1999.
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