The tops of the waves move faster than their bottoms do, which causes them to rise precipitously. When it does, it produces a vacuum effect that sucks coastal water seaward and exposes harbor and sea floors. Recognizing this phenomenon can save lives. A tsunami is usually composed of a series of waves, called a wave train, so its destructive force may be compounded as successive waves reach shore.
People experiencing a tsunami should remember that the danger may not have passed with the first wave and should await official word that it is safe to return to vulnerable locations. Some tsunamis do not appear on shore as massive breaking waves but instead resemble a quickly surging tide that inundates coastal areas.
The best defense against any tsunami is early warning that allows people to seek higher ground. The Pacific Tsunami Warning System, a coalition of 26 nations headquartered in Hawaii, maintains a web of seismic equipment and water level gauges to identify tsunamis at sea.
Similar systems are proposed to protect coastal areas worldwide. A supercell thunderstorm strikes in South Dakota. Among the most severe storms, supercells can bring strong winds, hail, and even tornadoes. See more extreme weather pictures. All rights reserved.
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Seismology What is a seismic wave? What is the difference between body waves and surface waves, and between P-waves and S-waves? Why can't S-waves travel through liquids? How far can seismic waves reach? Why do P-waves travel faster than S-waves? That is not the case with tsunamis generated by great earthquakes in the North Pacific or along the Pacific coast of South America.
On the average of about half-a-dozen times per century, a tsunami from one of these regions sweeps across the entire Pacific, is reflected from distant shores, and sets the entire ocean in motion for days. For example, the Chilean tsunami caused death and destruction throughout the Pacific. Hawaii, Samoa, and Easter Island all recorded runups exceeding 4 m; 61 people were killed in Hawaii. In Japan people died. There may not always be enough time for an official warning, so it is important to understand natural warnings.
Learn how to get alerts from the Tsunami Warning Centers. A tsunami is one the most powerful and destructive natural forces. It can produce unusually strong currents, rapidly flood land, and devastate coastal communities. Low-lying areas such as beaches, bays, lagoons, harbors, river mouths, and areas along rivers and streams leading to the ocean are the most vulnerable.
Most tsunami damage and destruction is caused by flooding, wave impacts, strong currents, erosion, and debris. The water can be just as dangerous as it returns to the sea, taking debris and people with it.
In addition to loss of life and mass injuries, other potential impacts include damage to and destruction of homes and businesses, cultural and natural resources, infrastructure, and critical facilities. Flooding and dangerous currents can last for days. Even small tsunamis can pose a threat. Strong currents can injure and drown swimmers and damage and destroy boats in harbors.
Local tsunamis are particularly dangerous. They can strike a coast within minutes of generation with little or no warning. Although tsunamis cannot be prevented, there are things you can do before a tsunami that could save your life and the lives of your family and friends.
Importantly, find out if your home, school, workplace, or other places you visit often are in a tsunami hazard zone U.
If you live or spend time in a tsunami hazard zone: Educate yourself about tsunami warnings official and natural and ensure you have multiple ways to receive official warnings. In the United States, get a NOAA Weather Radio , sign up for text message alerts from your local government, and verify that your mobile devices receive wireless emergency alerts. Make an emergency plan that includes plans for family communication and evacuation. Map out routes from home, work, and other places you visit often to safe places on high ground or inland away from the water and outside the tsunami hazard zone.
Your community may already have identified evacuation routes and assembly areas if they have not, identify a safe place at least feet above sea level or 1 mile inland. Plan to evacuate on foot if you can; roads may be impassable due to damage, closures, or traffic jams.
Practice walking your routes, even in darkness and bad weather. This will ease evacuation during an emergency. Put together a portable disaster supplies kit with items you and your family including pets may need in an emergency. Prepare kits for work and cars, too. Be a role model. Share your knowledge and plans with others. If you are visiting the coast, find out about local tsunami safety. Your hotel or campground should have this information. There are two ways that you may be warned that a tsunami is coming: an official tsunami warning and a natural tsunami warning.
Both are equally important. You may not get both. It may also come through outdoor sirens, local officials, emails and text message alerts from state and local opt-in systems, and telephone notifications. There may not always be time to wait for an official tsunami warning. A natural tsunami warning may be your first, best, or only warning that a tsunami is on its way. Natural tsunami warnings include strong or long earthquakes, a loud roar like a train or an airplane from the ocean, and unusual ocean behavior.
The ocean could look like a fast- rising flood or a wall of water bore. Or, it could recede suddenly, showing the ocean floor, reefs, and fish like a very low, low tide. If you experience any of these warnings, even just one, a tsunami could be coming. How you should respond to a tsunami warning depends on where you are and the type of warning you receive i.
Be prepared to respond immediately to whatever you hear or see first. If you are in a tsunami hazard zone and receive an official tsunami warning: Stay out of the water and away from beaches and waterways. Get more information from radio, television, or your mobile device text or data and continue to stay informed throughout the event. If officials ask you to evacuate, implement your emergency plan and move quickly to your safe place.
If you do not have a safe place or cannot reach it, follow evacuation signs to safety or go as high or as far inland away from the water as possible at least feet above sea level or a mile inland. If you are in a tsunami hazard zone and receive a natural tsunami warning, a tsunami could arrive within minutes: In case of an earthquake, protect yourself. Drop, cover, and hold on. Be prepared for aftershocks. Each time the earth shakes, drop, cover, and hold on.
Take action. Do not wait for an official warning or instructions from officials. As soon as you can move safely, implement your emergency plan and move quickly to your safe place. If there is earthquake damage, avoid fallen power lines and stay away from weakened structures. When you are in a safe place, get more information from radio, television, or your mobile device text or data. If you are on the beach or near water and feel an earthquake of any size and length, move quickly to high ground or inland away from the water as soon as you can move safely.
Get more information from radio, television, or your mobile device text or data. If you are outside of the tsunami hazard zone and receive a warning, stay where you are unless officials tell you otherwise.
For your safety and others, always follow instructions from local officials and stay out of the tsunami hazard zone until they tell you it is safe. In the United States, to find out if you are in a tsunami hazard zone, visit the Tsunami Maps web page.
For all U. In the unique case of a tsunami warning issued for local Hawaii earthquakes, the Pacific Tsunami Warning Center decides whether evacuations are necessary. When they are, local and state emergency management officials coordinate them and are responsible for determining when it is safe for people to return to an evacuated area. Most buildings are not designed to withstand tsunami impacts. However, the upper stories of some strong e.
If you are concerned that you will not be able to reach a safe place in time, ask your local emergency management office or hotel staff about vertical evacuation. Note, this type of evacuation is not recommended in all areas. If you are on a boat and you get a tsunami warning, your response will depend largely on where you are.
In the United States, in general, it is recommended that: If you are in a harbor and get a tsunami warning, you should leave your boat and move quickly to a safe place on land high ground or inland, away from the water.
Your harbor master, port captain, the U. Coast Guard, and local and state emergency management offices are the best sources for safe depth and other tsunami safety information and regulations for boaters in your area. If you are a boat owner or captain, take extra steps to prepare for a tsunami: Make sure you have a way to receive tsunami warnings when you are on the water.
Make a plan and put together a disaster supplies kit to keep on board your boat. Be aware that shore facilities may be damaged, so if you are at sea during a tsunami, you may not be able to return to the harbor you left. Be prepared to remain at sea for a day or more.
Tsunami Warning System.
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