How Far Does a Tsunami Travel? Understanding Tsunami Travel Distance

Are you curious about tsunamis and their potential impact on travel plans to Vietnam? The distance a tsunami travels is a crucial factor in understanding its effects. SIXT.VN is here to help you understand tsunami travel and stay informed about travel safety in Vietnam. With proper knowledge and preparation, you can ensure a safe and enjoyable trip. Learn more about travel advisory and disaster preparedness!

1. General Tsunami Information

1.1 What is a Tsunami?

A tsunami is a series of extremely long ocean waves caused by large, sudden disturbances, as stated by the National Weather Service. These waves can travel vast distances, impacting coastal regions far from the source. When planning trips, especially to coastal regions in Vietnam, understanding these natural phenomena is crucial.

1.2 What is the Origin of the Word “Tsunami?”

The word tsunami comes from Japanese, combining the characters for “harbor” (tsu) and “wave” (nami). This reflects the historical impact of these waves on coastal communities.

1.3 Is a Tsunami the Same as a Seismic Sea Wave or a Tidal Wave?

A tsunami is a seismic sea wave if generated by an earthquake. However, tsunamis can also arise from non-seismic events. Tsunamis are unrelated to tides, which are caused by the gravitational pull of the Sun and Moon. So, calling a tsunami a tidal wave is incorrect.

1.4 Can Tsunamis Be Predicted?

While scientists cannot predict exactly when and where a tsunami will occur, Tsunami Warning Centers monitor earthquakes likely to generate tsunamis. They use forecast models to estimate wave height, arrival times, and potential flooding. Travelers should recognize natural warnings and stay prepared, especially in coastal regions.

1.5 How Often Do Tsunamis Happen?

Tsunamis causing damage or deaths near their source occur about twice per year. Those affecting distant shores happen approximately twice per decade, according to the Global Historical Tsunami Database.

1.6 Where Do Tsunamis Happen?

Tsunamis can occur in any large body of water, including oceans and inland seas. Certain areas are more prone due to their proximity to tsunami sources, bathymetry, and topography. The Pacific Ocean, particularly around the “Ring of Fire,” experiences the majority of these events.

According to the Global Historical Tsunami Database, between 1900 and 2015:

• About 78% occurred in the Pacific Ocean.
• 8% in the Atlantic Ocean and Caribbean Sea.
• 6% in the Mediterranean Sea.
• 5% in the Indian Ocean.
• 1% in other seas.

Since 1900, Japan has had the highest percentage of tsunamis (21%), followed by Russia and Indonesia (8% each).

1.7 Where Can Tsunamis Happen in the United States?

Any U.S. coast can be struck by a tsunami, but the hazard level varies. Coastlines near subduction zones, like those around the Pacific and Caribbean, face the greatest risk.

1.7.1 What is the Tsunami Hazard Level for Anchorage and the Upper Cook Inlet in Alaska?

The tsunami hazard level for Anchorage and the upper Cook Inlet is very low compared to the Southern Coast of Alaska. The shallow waters weaken tsunamis entering the upper Cook Inlet, reducing their danger.

1.8 What Are Some of the Most Damaging Tsunamis to Affect the United States?

As of January 2018, 30 reported tsunamis have caused at least one death or $1 million in damage (2017 dollars) in U.S. states and territories, according to the Global Historical Tsunami Database.

*See below: “What is the difference between a local and a distant tsunami?”

1.9 When Do Tsunamis Happen?

Tsunamis can happen any time, in any season, and during any weather. There is no specific tsunami season.

1.10 Where Can I Learn More About Tsunamis?

Numerous online resources provide more information about tsunamis, including:

1. The COMET Program’s Tsunami Distance Learning Course.
2. National Weather Service’s JetStream Online Weather School.
3. National Weather Service’s Tsunami Safety website.
4. International Tsunami Information Center.
5. Global Historical Tsunami Database.
6. The TsunamiZone.

2. Causes of a Tsunami

2.1 What Causes a Tsunami?

A tsunami is caused by a large and sudden displacement of the ocean. Earthquakes are the most common cause, but landslides, volcanic activity, weather, and near-Earth objects can also cause them. Most tsunamis (88%) in the Global Historical Tsunami Database were generated by earthquakes or landslides caused by earthquakes.

2.2 How Do Earthquakes Generate Tsunamis?

Earthquakes generate tsunamis through sudden movements in the water column. The location, magnitude, and depth of an earthquake are crucial factors. Most tsunamis are generated by earthquakes with magnitudes over 7.0 that occur under or very near the ocean and less than 100 kilometers (62 miles) below the Earth’s surface. Generally, an earthquake must exceed magnitude 8.0 to generate a dangerous distant tsunami.

Key factors for tsunami generation include:

• Magnitude: Earthquakes above magnitude 7.0 are more likely to cause tsunamis.
• Location: Earthquakes occurring under or near the ocean are more dangerous.
• Depth: Shallow earthquakes (less than 100 km deep) are more likely to cause tsunamis.

Examples of earthquake-generated tsunamis:

1. March 11, 2011, Honshu Island, Japan: A magnitude 9.1 earthquake generated a tsunami that caused tremendous devastation locally and was observed all over the Pacific.
2. December 26, 2004, Northern Sumatra, Indonesia: A magnitude 9.1 earthquake generated the deadliest tsunami in history, impacting 15 countries in Southeastern and Southern Asia and Eastern and Southern Africa.
3. March 27, 1964, Prince William Sound, Alaska: A magnitude 9.2 earthquake (the largest recorded in U.S. history) generated tsunamis that devastated coastal communities in Alaska.
4. April 1, 1946, Aleutian Islands, Alaska: A magnitude 8.6 earthquake generated a tsunami that was destructive across the Pacific, particularly in Hawaii.
5. November 1, 1755, Lisbon, Portugal: A magnitude 8.5 (estimated) earthquake in the Atlantic Ocean generated a tsunami that affected the coasts of Portugal, Spain, North Africa, and the Caribbean.
6. January 26, 1700, Cascadia Subduction Zone: A magnitude 9.0 (estimated) earthquake generated a tsunami that inundated the coasts of Cascadia (northern California, Oregon, Washington, and southern British Columbia) and Japan.

2.2.1 What Types of Earthquakes Generate Tsunamis?

Most tsunami-generating earthquakes occur on thrust or reverse faults in subduction zones. However, 10-15 percent are generated by strike-slip earthquakes, which usually affect nearby regions due to associated landslides.

2.2.2 What Was the Largest Earthquake Ever Recorded?

The largest earthquake ever recorded was a magnitude 9.5 earthquake off the coast of Southern Chile on May 22, 1960.

2.3 How Do Landslides Generate Tsunamis?

Landslides, including rock falls, slope failures, and glacial calving, can generate tsunamis when they displace water. These tsunamis may be larger than seismic tsunamis near their source but lose energy quickly and rarely affect distant coastlines.

Examples of landslide-generated tsunamis:

1. July 17, 1998, Papua New Guinea: A magnitude 7.0 earthquake triggered a large underwater landslide, generating a deadly tsunami.
2. July 10, 1958, Southeast Alaska: A magnitude 7.8 earthquake triggered landslides, rock falls, and ice falls that generated tsunamis, including the largest tsunami ever recorded in Lituya Bay.
3. November 18, 1929, Grand Banks, Newfoundland, Canada: A magnitude 7.3 earthquake triggered a submarine landslide that generated a tsunami.

2.4 How Do Volcanoes Generate Tsunamis?

Volcanic activity can displace enough water to generate tsunamis, including:

1. Pyroclastic flows
2. Submarine explosions
3. Caldera formation
4. Landslides
5. Lateral blasts

Volcanic tsunamis usually lose energy quickly and rarely affect distant coastlines.

Examples of volcano-generated tsunamis:

1. August 27, 1883, Indonesia: The volcano Krakatau exploded and collapsed, generating one of the largest and most destructive tsunamis ever recorded.
2. May 21, 1792, Kyushu Island, Japan: A flank collapse at the end of the Unzen volcano’s eruption generated a tsunami.
3. ~1610 BC, Greece: The volcano Santorini (Thera) erupted, generating a tsunami that swept the shores of nearby islands.

2.5 How Does Weather Generate Tsunamis?

Air pressure disturbances, often associated with fast-moving weather systems, can generate meteotsunamis. These are similar to earthquake-generated tsunamis and depend on the intensity, direction, and speed of the air pressure disturbance.

Examples of meteotsunamis:

1. June 13, 2013, Northeastern United States: Tsunami-like waves crashed upon the New Jersey and southern Massachusetts coasts due to a derecho (a high-speed windstorm).
2. June 21, 1978, Vela Luka, Croatia: Flooding waves inundated the port town of Vela Luka due to an atmospheric disturbance, identified as the strongest meteotsunami on record.

2.6 Can Near-Earth Objects Generate Tsunamis?

It is rare for near-Earth objects to reach the Earth, but they can potentially generate tsunamis. Large objects could cause “impact” tsunamis, while smaller objects exploding in the atmosphere could cause “airburst” tsunamis.

One notable example is the Chicxulub impact on Mexico’s Yucatán Peninsula, which likely caused a mass extinction and may have generated a tsunami that reached hundreds of miles inland around the Gulf of America.

3. Tsunami Characteristics

3.1 How Many Waves Are There in a Tsunami?

A tsunami is a series of waves, often called the tsunami wave train. A large tsunami may continue for days in some locations.

3.2 How Far Does a Tsunami Travel?

The distance a tsunami travels depends on the depth of the water. In the deep ocean, tsunamis can travel as fast as a jet plane, over 500 mph, and cross entire oceans in less than a day. As they enter shallow water near land, they slow to the speed of a car, approximately 20 or 30 mph.

Tsunami speed is computed by taking the square root of the product of the water depth and the acceleration of gravity (32.2 feet per second squared). In 15,000 feet of water, this works out to about 475 miles per hour. At these rates, a tsunami will travel from the Aleutian Islands to Hawaii in about five hours, or from the Portugal coast to North Carolina in eight and a half hours.

SIXT.VN advises travelers to always check local tsunami warnings and be prepared when visiting coastal areas.

3.3 How Big Is a Tsunami?

In the deep ocean, tsunami waves may be barely noticeable and rarely more than three feet high. As they enter shallow water near land, they grow in height, and currents intensify. When they strike land, most tsunamis are less than 10 feet high, but in extreme cases, can exceed 100 feet near their source.

Offshore and coastal features can affect how a tsunami impacts coasts differently. Reefs, bays, entrances to rivers, undersea features, and the slope of the beach can influence the size, appearance, and impact of tsunamis.

3.4 What Does a Tsunami Look Like When It Reaches the Coast?

When a tsunami reaches the coast, it may look like a fast-rising flood or a wall of water. Its appearance may differ at different points along a coast and will not look like a normal wind wave. Sometimes, before the water rushes on land, it will suddenly recede, showing the ocean floor, reefs, and fish.

3.5 How Long Does a Tsunami Last?

Large tsunamis may continue for days in some locations, reaching their peak often a couple of hours after arrival and gradually tapering off after that. The time between tsunami crests ranges from approximately five minutes to two hours. Dangerous tsunami currents can last for days.

3.6 What Is the Difference Between a Local and a Distant Tsunami?

Tsunamis are often referred to as local or distant, depending on the location of their source. A local tsunami originates close to the coast and may arrive in less than one hour, making warning time limited. A distant tsunami is generated far away from a coast, allowing more time to issue and respond to warnings.

3.7 How Are Tsunamis Different From Normal Ocean Waves?

Most ocean waves are generated by wind, whereas tsunamis are caused by earthquakes, landslides, or volcanic activity. Tsunamis move through the entire water column, while wind waves only affect the ocean surface.

4. Tsunami Detection and Forecasting

4.1 What Are the Responsibilities of the Tsunami Warning Centers?

The National Weather Service (NWS) operates two Tsunami Warning Centers that monitor observational networks, analyze earthquakes, evaluate water-level information, issue tsunami messages, conduct public outreach, and coordinate with organizations to continually improve their operations.

4.2 How Are Tsunamis Detected?

Tsunami Warning Centers rely on seismic and water-level networks worldwide to determine when and where to issue tsunami messages:

1. Seismic Networks: Provide information about an earthquake’s location, depth, magnitude, and other characteristics.
2. Water-Level Networks: Include Deep-ocean Assessment and Reporting of Tsunami (DART) systems and coastal water-level stations to detect changes in water-level height.

4.3 What is a DART System?

DART (Deep-ocean Assessment and Reporting of Tsunami) systems are developed by NOAA for early detection, measurement, and real-time reporting of tsunamis in the open ocean. These systems consist of a bottom pressure recorder (BPR) anchored on the ocean floor and a surface buoy.

4.4 What is a Coastal Water-Level Station?

Coastal water-level stations collect information about the height of the ocean at specific coastal locations. They monitor tides for navigation and relay information to warning centers to confirm tsunami arrival time and height.

4.5 How Are Tsunamis Forecast?

In most cases, the first sign of a potential tsunami is an earthquake. Seismic waves travel faster than tsunamis, providing early information. Three key pieces of information about an earthquake help the Tsunami Warning Centers determine if it was capable of generating a tsunami: location, depth, and magnitude. The warning centers use this preliminary seismic information to decide if they should issue a tsunami message.

Once a message is issued, the warning centers conduct additional seismic analysis and run tsunami forecast models using information from the seismic and water-level networks.

5. Tsunami Messages

5.1 What Are Tsunami Messages?

Tsunami messages are issued by the Tsunami Warning Centers to notify emergency managers, the public, and other partners about the potential for a tsunami. These messages include alerts, such as warning, advisory, watch, and information statement.

5.1.1 What Is a Tsunami Warning?

A tsunami warning is issued when a tsunami with the potential to generate widespread inundation is imminent, expected, or occurring. Warnings alert the public that dangerous coastal flooding accompanied by powerful currents is possible.

5.1.2 What Is a Tsunami Advisory?

A tsunami advisory is issued when a tsunami with the potential to generate strong currents or waves dangerous to those in or very near the water is imminent, expected, or occurring. Significant inundation is not expected for areas under an advisory.

5.1.3 What Is a Tsunami Watch?

A tsunami watch is issued when a tsunami may later impact the watch area. The watch may be upgraded to a warning or advisory or canceled based on updated information.

5.1.4 What Is a Tsunami Information Statement?

A tsunami information statement is issued when an earthquake or tsunami has occurred of interest to the message recipients. In most cases, information statements indicate there is no threat of a destructive basin-wide tsunami and prevent unnecessary evacuations.

5.2 What Is a Tsunami Threat Message?

A tsunami threat message is a tsunami message for international partners in the Pacific and Caribbean. The purpose of these messages is to help national authorities understand the threat to their coasts so they can determine which alerts to issue.

5.3 Who Issues Tsunami Messages?

The Tsunami Warning Centers prepare and issue tsunami messages for their respective designated service areas. Primary recipients include NWS Weather Forecast Offices, state emergency operations centers, the U.S. Coast Guard, the U.S. military, and designated international authorities.

5.4 Who Cancels Tsunami Messages?

The Tsunami Warning Centers issue a cancellation after they determine that a destructive tsunami will not affect an area under a warning, advisory, or watch, or that a tsunami has diminished to a level where additional damage is not expected.

5.5 What Are the Designated Service Areas of the Tsunami Warning Centers?

1. The National Tsunami Warning Center in Palmer, Alaska, serves the continental United States, Alaska, and Canada.
2. The Pacific Tsunami Warning Center in Honolulu, Hawaii, directly serves the Hawaiian Islands, the U.S. Pacific and Caribbean territories, and the British Virgin Islands and is the primary international forecast center for the warning systems in the Pacific and the Caribbean and Adjacent Regions.

5.6 How Do the Tsunami Warning Centers Decide What Alert Levels to Include in Their Messages?

The Tsunami Warning Centers base their initial tsunami messages on the preliminary earthquake information received from seismic networks. They use preset criteria to decide when to issue a tsunami message and what alert(s) to include. Subsequent messages and alerts are based on impact estimation resulting from additional seismic analysis, water-level measurements, tsunami forecast model results, and historical tsunami information.

5.7 How Quickly Are Tsunami Messages Issued?

The time it takes for a Tsunami Warning Center to issue a tsunami message depends on the seismic network density and distribution near the earthquake’s point of origin. In regions of high seismic network density, the warning centers can issue messages within five minutes. In areas of lower seismic network density, response time increases to 10-15 minutes.

5.8 How Can I Receive Tsunami Messages?

In the United States, tsunami messages are broadcast through local radio and television, marine radio, wireless emergency alerts, NOAA Weather Radio, NOAA websites, and social media accounts.

6. Tsunami Safety

6.1 Why Are Tsunamis Dangerous?

A tsunami is one of the most powerful and destructive natural forces. It can produce unusually strong currents, rapidly flood land, and devastate coastal communities. Low-lying areas are the most vulnerable.

6.2 How Can I Prepare for a Tsunami?

Although tsunamis cannot be prevented, there are things you can do before a tsunami that could save your life:

1. Find out if your home, school, workplace, or other places you visit often are in a tsunami hazard zone.
2. Educate yourself about tsunami warnings and ensure you have multiple ways to receive official warnings.
3. Make an emergency plan that includes plans for family communication and evacuation.
4. Map out routes from home, work, and other places you visit often to safe places on high ground or inland.
5. Practice walking your routes, even in darkness and bad weather.
6. Put together a portable disaster supplies kit.
7. Be a role model by sharing your knowledge and plans with others.

6.3 How Will I Know If a Tsunami Is Coming?

There are two ways that you may be warned that a tsunami is coming: an official tsunami warning and a natural tsunami warning.

1. An official tsunami warning will be broadcast through local radio and television, marine radio, wireless emergency alerts, NOAA Weather Radio, and NOAA websites and social media accounts.
2. 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 from the ocean, and unusual ocean behavior.

6.4 How Should I Respond to a Tsunami Warning?

How you should respond to a tsunami warning depends on where you are and the type of warning you receive:

• If you are in a tsunami hazard zone and receive an official tsunami warning:
  1. Stay out of the water and away from beaches and waterways.
  2. Get more information from radio, television, or your mobile device.
  3. If officials ask you to evacuate, implement your emergency plan and move quickly to your safe place.
• If you are in a tsunami hazard zone and receive a natural tsunami warning:
  1. Protect yourself during the earthquake. Drop, cover, and hold on.
  2. Take action. Do not wait for an official warning.
  3. Implement your emergency plan and move quickly to your safe place.
• 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.

6.5 Who Issues Tsunami Evacuation Orders?

For all U.S. states and territories, evacuation requests are typically issued and coordinated by local emergency management officials.

6.6 Will I Be Safe From a Tsunami in a Tall Building?

Most buildings are not designed to withstand tsunami impacts. However, the upper stories of some strong and tall buildings may provide protection if no other options are available. Ask local emergency management or hotel staff about vertical evacuation.

6.7 What Do I Do If I Am in a Boat in a Harbor or at Sea During a Tsunami?

If you are on a boat and get a tsunami warning:

• If you are in a harbor, leave your boat and move quickly to a safe place on land.
• If you are at sea, move to a safe depth and stay away from harbors under warning until officials tell you the threat has passed.

Understanding how far a tsunami travels and the measures to take in case of such an event are crucial for ensuring safety, especially when planning trips to coastal regions like Vietnam. SIXT.VN is committed to providing you with up-to-date information and reliable services to make your travel experience safe and enjoyable.

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Hotline/WhatsApp: +84 986 244 358
Website: SIXT.VN

FAQ about Tsunamis:

1. How are tsunamis formed?
   • Tsunamis are typically caused by large-scale underwater disturbances such as earthquakes, volcanic eruptions, or landslides, which displace a large volume of water.
2. What should I do if a tsunami warning is issued?
   • If you are in a coastal area and a tsunami warning is issued, immediately evacuate to higher ground or inland, away from the coast.
3. How fast can tsunamis travel?
   • In the deep ocean, tsunamis can travel at speeds of up to 500 mph (805 km/h), similar to a jet plane.
4. Are there any natural signs of an approaching tsunami?
   • Natural signs include a strong earthquake, a sudden rise or fall in sea level, and a loud roar coming from the ocean, even if the sea appears calm.
5. What is the difference between a tsunami watch and a tsunami warning?
   • A tsunami watch means a tsunami is possible, so people should be prepared, while a tsunami warning means a tsunami is imminent or expected, requiring immediate evacuation.
6. How can I stay informed about tsunami warnings?
   • Stay tuned to local news channels, radio stations, and official government alerts, as well as monitoring apps and websites provided by meteorological agencies.
7. Is it safe to go back to the coast after the first wave of a tsunami?
   • No, tsunamis consist of a series of waves that can continue for several hours. It is essential to stay away from the coast until officials declare it safe to return.
8. Can small tsunamis still be dangerous?
   • Yes, even small tsunamis can generate strong currents that can be hazardous to swimmers and damage boats in harbors.
9. Where are tsunamis most common?
   • Tsunamis are most common in the Pacific Ocean, especially in areas around the “Ring of Fire,” where many earthquakes and volcanic eruptions occur.
10. How do scientists predict tsunamis?
    • Scientists use seismic data, deep-ocean buoys (DART systems), and coastal tide gauges to detect and forecast tsunamis, as well as computer models to estimate their potential impact on coastal areas.