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A tsunami (pronounced soonahmee) is a series of sea waves most commonly cause by an earthquake beneath the sea floor. In the open ocean, tsunami waves travel at speeds of up to 600 miles per hour. As the waves enter shallow water, they may rise rapidly.
The waves can kill and injure people and cause great property damage where they come ashore. The first wave is often not the largest; successive waves may be spaced many minutes apart and continue to arrive for several hours.
 Locally generated tsunami - If a large earthquake displaces the sea floor near the coast, the first wave may reach shore minutes after the ground stops shaking. There is no time for authorities to issue a warning.
Distant source tsunami - Tsunami waves may reach the coast hours after an earthquake far out in the Pacific Ocean. The West Coast / Alaska Tsunami Warning Center alerts local officials who may not receive official announcements. If you notice a sudden drop or rise in sea level, it may be a warning of impending danger. Move to high ground immediately.
Where and when do tsunamis occur?
Tsunamis can occur at any time of day or night, under any and all weather conditions, and in all seasons. Beaches open to the ocean, by mouths of bays or tidal flats, and the shores of large coastal rivers are especially vulnerable to tsunamis.
How do I know when to evacuate?
A strong off-shore earthquake may generate a tsunami. Therefore, if you feel the ground shake, evacuate to high ground immediately and return only after officials say it is safe to do so.
During distant source tsunami events, local emergency management officials will advise citizens to evacuate by making an announcement over the emergency alert system.
What is low-lying area and how high is high ground?
Typical peak wave heights from large tsunamis in the Pacific Ocean over the last 80 years have been between 21 and 45 feet at the shoreline. A few waves have been higher, is isolated locations as high as 100 feet. The best general advise today is to: g:o to an area 50 feet above sea level, if possible. If you are on the beach and unable to get this high, go as high and far inland as you can.
Go on foot if possible, particularily if local damage resulting from an earthquake has caused damage to roads, power line, and resulted in significant earthquake debris.
What can I do to protect myself from a tsunami?
Make disaster plans now. Family members need to know what to do on their own to protect themselves from an earthquake or tsunami. Take a first aid course and learn survival skills. Talk with family, friends, and neighbors. Knowledge is your greatest defense against potential disaster.
Be familiar with local emergency management earthquake and tsunami plans. Know where to go to survive a tsunami. Never go to the coast to watch a tsunami. Tsunamis may move faster than a person can run. If you see an unexpected rise or fall in the coastal water a tsunami may be approaching. Do not wait - instead move inland or uphill as quickly as possible.
Do not return to shore after the first wave. A tsunami is a series of waves and many times the second or third wave is bigger than the first. Waves may continue for several hours. Wait for Emergeny Management Officials to tell you the danger has passed.
Assemble a portable disaster supply kit. Be prepared to survive on your own for minimum of three days in the event of an earthquake or tsunami.Have a kit in your car, at home, and at work. Your kit should include a portable radio with fresh batteries, water, first aid supplies, flashlight, and extra clothes or a blanket. Put your kit in a backpack and leave it in a convenient location.
If you are camping on or near the beach, you may have to abandon your campsite to go inland or to higher ground to save your life.
Stay tuned to your radio, marine radio, or NOAA weather radio during a tsunami emergency. Bulletins will be issued regularly through your local Emergency Management and National Weather Service offices.
What should you do if you feel a strong earthquake when you are on the coast?
Drop, cover, and hold. Get under a sturdy object and hold on. Watch for falling objects. As soon as the shaking is over, move to high ground or inland. Do not wait for on official warning.
Stay away from the coast. Waves may continue to arrive for hours.
Listen to your radio for an official "all clear" before returning to the coastal area.
Be alert for aftershocks.
Who gives official tsunami warnings?
The West Coast Alaska Tsunami Warning Center is responsible for issuing warnings abour pitential tsunamis along the west coast of the United States. Bulletins are issued within 10 - 15 minutes of large undersea earthquakes in the pacific basin. The information is transmitted to state and local emergency managers: they decide whether to order an evacuation.
For additional information about Tsunamis contact:
International Tsunami Information Center
Box 50027
Honolulu, HI, 96850-4993 - Tel. 808-532-6423 |
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