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TSUNAMI
Produced by the National Disaster Education
Coalition:
American Red Cross, FEMA, IAEM, IBHS, NFPA, NWS, USDA/CSREES,
and USGS. |
Why Talk About Tsunamis?
Twenty-four tsunamis have caused damage in the United States and
its territories during the last 204 years. Just since 1946, six
tsunamis have killed more than 350 people and caused a half billion
dollars 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, tens of feet, and can cause great loss of life and
property damage when it comes ashore. Tsunamis can travel upstream
in coastal estuaries and rivers, with damaging waves extending
farther inland than the immediate coast. A tsunami can occur during
any season of the year and at any time, day or night.
Since 1946, six
tsunamis have killed more than 350 people and damaged a half billion
dollars of property in Hawaii, Alaska, and the West Coast.
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What Are Tsunamis,
and What Causes Them?
Tsunamis are ocean waves produced by earthquakes or underwater
landslides. The word is Japanese and means "harbor wave,"
because of the devastating effects these waves have had on low-lying
Japanese coastal communities. Tsunamis are often incorrectly
referred to as tidal waves, but a tsunami 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 hundreds of miles
long, with an amplitude of only a few feet. This would also make
them unnoticeable from the air. As the waves approach the coast,
their speed decreases and their amplitude increases. Unusual wave
heights 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 injuries.
Tsunamis are most often generated by earthquake-induced
movement of the ocean floor. Landslides, volcanic eruptions, and
even meteorites can also generate a tsunami. If a major earthquake
is felt, a tsunami could reach the beach in a few minutes, even
before a warning is issued. Areas at greatest risk are less than 25
feet above sea level and within one mile of the shoreline. Most
deaths caused by a tsunami are because of drowning. Associated risks
include flooding, contamination of drinking water, fires from
ruptured tanks or gas lines, and the loss of vital community
infrastructure (police, fire, and medical facilities).
From an initial tsunami generating source area, waves travel
outward in all directions much like the ripples caused by throwing a
rock into a pond. As these waves approach coastal areas, the time
between successive 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. Furthermore, one coastal community may
experience no damaging waves while another, not 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 contacting
your local emergency management office, National Weather Service
office, or
American Red Cross chapter. If you are in a tsunami risk area,
learn how to protect yourself, your family, and your property.
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Awareness Information
The West
Coast/Alaska Tsunami Warning Center (WC/ATWC) is responsible for
tsunami warnings for 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.
territories within the Pacific basin. The two Tsunami Warning
Centers coordinate the information being disseminated.
All tsunamis are potentially dangerous, even though they may not
damage every coastline they strike. Damaging tsunamis are very rare.
Our coastlines are vulnerable, but tsunamis are infrequent.
Understand the hazard and learn how to protect yourself, but don't
let the threat of tsunamis ruin your enjoyment of the beach.
The WC/ATWC and PTWC may issue the following bulletins:
- WARNING: A
tsunami was or may have been generated, which could cause damage;
therefore, people in the warned area are strongly advised to
evacuate.
- 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 should
prepare for possible evacuation if their area is upgraded to a
warning.
- ADVISORY: An earthquake has occurred in the
Pacific basin, which might generate a tsunami. WC/ATWC and PTWC
will issue hourly bulletins advising of the situation.
- INFORMATION: A message with information about
an earthquake that is not expected to generate a tsunami. Usually
only one bulletin is issued.
Be familiar with the tsunami warning signs.
A strong earthquake lasting 20 seconds or more near the coast may
generate a tsunami. A noticeable rapid rise or fall in coastal
waters is also a sign that a tsunami is approaching.
Tsunamis most frequently come onshore as a rapidly rising
turbulent surge of water choked with debris. They are not V-shaped
or rolling waves, and are not "surfable."
Tsunamis may be locally generated or from a
distant source. In 1992, the Cape Mendocino, California,
earthquake produced a tsunami that reached Eureka in about 20
minutes, and Crescent City in 50 minutes. Although this tsunami had
a wave height of about one foot and was not destructive, it
illustrates how quickly a wave can arrive at nearby coastal
communities 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.
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Plan for a Tsunami
Develop a Family Disaster Plan.
Please see the "Family
Disaster Plan" section for general family planning information.
Tsunami-specific planning should include the following:
- 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 or other frequently visited locations are in tsunami
hazard areas. Know the height 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 these numbers.
- If you are visiting an
area at risk from tsunamis, check with the hotel, motel, or
campground operators for tsunami evacuation information and how
you would be warned. It is important to know designated
escape routes 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, pick an
area 100 feet above sea level or go up to two miles inland, away
from the coastline. If you can't get this high or far, go as high
as you can. Every foot inland or upwards may make a difference.
You should be able to reach your safe location on foot within 15
minutes. After a disaster, roads may become impassable or blocked.
Be prepared to evacuate by foot if necessary. Footpaths normally
lead uphill and inland, while many roads parallel coastlines.
Follow posted tsunami evacuation routes; these will lead to
safety. Local emergency management officials can help advise you
as to the best route to safety and likely shelter locations.
- Practice your
evacuation route. Familiarity may save your life. Be
able to follow your escape route at night and during inclement
weather. 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 you informed of local
watches and warnings. The tone alert feature will warn
you of potential danger even if you are not currently listening to
local radio or television stations.
- Talk to your insurance
agent. Homeowners' policies do not cover flooding from
a tsunami. Ask about the National Flood Insurance Program.
- Discuss tsunami with
your family. Everyone 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 Supplies Kit!
Please see the section
"Disaster Supplies Kit"
for general supplies kit information. Tsunami-specific supplies
should include the following:
- Evacuation Supplies Kit in an easy-to-carry
container (backpack) near your door.
- Disaster Supplies Kit basics.
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How to Protect Your Property
- 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.
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Media and Community
Education Ideas
- If your community is at risk, build and
publicize locations of tsunami evacuation routes. Post signs
directing people to higher ground away from the coast.
- Review land use in tsunami hazard areas so no
critical facilities, such as hospitals and police stations; or
high occupancy buildings, such as auditoriums or schools; or
petroleum-storage tank farms are located where there is a tsunami
hazard. Tsunami damage can be minimized through land use planning,
preparation, and evacuation.
- Publish a special section in your local
newspaper with emergency information on tsunamis. Localize the
information by printing the phone numbers of local emergency
services offices, the American Red Cross chapter, and hospitals.
- Periodically inform your community of local
public warning systems.
- Work with local emergency services and
American Red Cross officials to prepare special reports for people
with mobility impairments on what to do if an evacuation is
ordered, and develop plans to assist them with evacuation if
necessary.
- Interview local officials and insurance
companies about the proper types of insurance to cover a
flood-related loss. Include information on the economic effects of
disaster.
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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 first protect yourself from the
earthquake.
- When the shaking
stops, gather your family members and evacuate quickly.
Leave everything else behind. A tsunami may be coming within
minutes. Move quickly to higher ground away from the coast.
- Be careful to avoid downed power lines and
stay away from buildings and bridges from which heavy objects
might fall during an aftershock.
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What to Do When
a Tsunami WATCH is Issued
- Listen to a NOAA
Weather Radio, Coast Guard emergency frequency station, or other
reliable source for updated emergency information. As
the energy of a tsunami is transferred through open water, it is
not detectable. Seismic action may be the only advance warning
before the tsunami approaches the coastline.
- Check your Disaster
Supplies Kit. Some supplies may need to be replaced or
restocked.
- Locate family members
and review evacuation plans. Make sure everyone knows
there is a potential threat and the best way to safer ground.
- If you have special
evacuation needs (small children, elderly people, or persons with
disabilities) consider early evacuation. Evacuation may
take longer, allow extra time.
- If time permits,
secure unanchored objects around your home or business.
Tsunami waves can sweep away loose objects. Securing these items
or moving them inside will reduce potential loss or damage.
- Be ready to evacuate.
Being prepared will help you to move more quickly if a tsunami
warning is issued.
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What to Do
When a Tsunami WARNING is Issued
- Listen to a NOAA
Weather Radio, Coast Guard emergency frequency station, or other
reliable source for updated emergency information.
Authorities will issue a warning only if they believe there is a
real threat from tsunami.
- Follow instructions
issued by local authorities. Recommended evacuation
routes may be different from the one you use, or you may be
advised to climb higher.
- If you are in a tsunami risk area, do the
following:
- If you hear an official
tsunami warning or detect signs of a tsunami, evacuate at once.
A tsunami warning is issued when authorities are certain that a
tsunami threat exists, and there may be little time to get out.
- Take your Disaster
Supplies Kit. Having supplies will make you more
comfortable during the evacuation.
- Get to higher ground as
far inland as possible. Officials cannot reliably predict
either the height or local effects of tsunamis. Watching a
tsunami from the beach or cliffs could put you in grave danger.
If you can see the wave, you are too close to escape it.
Return home only after local officials
tell you it is safe. A tsunami is a series of waves that
may continue for hours. Do not assume that after one wave the danger
is over. The next wave may be larger than the first one.
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What to Do After a Tsunami
- Continue listening to
a NOAA Weather Radio, Coast Guard emergency frequency station, or
other reliable source for emergency information. The
tsunami may have damaged roads, bridges, or other places that may
be unsafe.
- Help injured or
trapped persons. Give first aid where appropriate. 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 assistance - infants, elderly people, and
people with disabilities. Elderly people and people
with disabilities may require additional assistance. People who
care for them or who have large families may need additional
assistance in emergency situations.
- Use the telephone only
for emergency calls. Telephone lines are frequently
overwhelmed in disaster situations. They need to be clear for
emergency calls to get through.
- Stay out of the
building if waters remain around it. Tsunami waters,
like flood waters, can undermine foundations, causing buildings to
sink, floors to crack, or walls to collapse.
- When re-entering
buildings or homes, use extreme caution. Tsunami-driven
flood waters may have damaged buildings where you least expect it.
Carefully watch every step you take.
- Wear sturdy shoes.
The most common injury following a disaster is cut feet.
- Use battery-powered
lanterns or flashlights when examining buildings.
Battery-powered lighting is the safest and easiest, preventing
fire hazard for the user, occupants, and building.
- Examine walls, floors,
doors, staircases, and windows to 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 broken or leaking gas lines, flooded electrical
circuits, or submerged furnaces or electrical appliances.
Flammable or explosive materials may come from upstream. Fire is
the most 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 using
the outside main valve if you can, and call the gas company from
a neighbor's 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
electricity at the main fuse box or circuit breaker. If you have
to step in water to get to the fuse box or circuit breaker, call
an electrician first for advice. Electrical equipment should be
checked and dried before being returned to service.
- Check for sewage and
water line damage. If you 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 tap. You can obtain safe water from undamaged
water heaters or by melting ice cubes.
- Use tap water if local
health officials advise it is safe.
- Watch out for animals,
especially poisonous snakes, that 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 that could fall.
- Take pictures of the
damage, both of the building and its contents, for insurance
claims.
- Open the windows and
doors to help dry the building.
- Shovel mud while it is
still moist to give walls and floors an opportunity to dry.
- Check food supplies.
Any food that has come in contact with flood waters may be
contaminated and should be thrown out.
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