|
Tsunami
Tsunami in PDF Format
-- 107 KB
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.
[Back to Top]
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.
[Back to Top]
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.
[Back to Top]
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 contanier (backpack) near
your door.
- Disaster Suplies Kit basics.
[Back to Top]
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.
[Back to Top]
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.
[Back to Top]
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.
[Back to Top]
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.
[Back to Top]
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.
[Back to Top]
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.
[Back to Top]
|
|