Houses above the inundation zone in this Japanese village survived intact, while everything below was destroyed by the 2011 tsunami. (Image credit: Patrick Corcoran, Oregon State University) Maybe the fastest man in the world could run a 6-minute mile for 6 miles (10 kilometers) while a terrifying wall of water chased him through a coastal city. But most people couldn’t. Yet a myth persists that a person could outrun a tsunami.
That’s just not possible, tsunami safety experts told LiveScience, even for Usain Bolt, one of the world’s quickest sprinters. Getting to high ground or high elevation is the only way to survive the monster waves.
«I try to explain to people that it doesn’t really matter how fast [the wave] is coming in, the point is that you really shouldn’t be there in the first place,» said Rocky Lopes of the National Oceanic and Atmospheric Administration’s Tsunami Mitigation, Education and Outreach program.
But because they didn’t know the warning signals, ignored them or just couldn’t get to safety in time, more than 200,000 people died in tsunamis in the past decade. And it’s not just tsunamis: Underestimating the power of the ocean kills thousands every year in hurricane storm surges.
Stay off the beachA tsunami is a series of waves caused by a sudden underwater earth movement. The kick-off is akin to dropping a big rock in a children’s pool filled with water. In an ocean basin, tsunami waves slosh back and forth, reflecting off coastlines, just like the (much smaller) waves in a child’s pool, Lopes said. Tsunamis gain height as they approach the shore. (Image credit: NOAA)Because many people mistakenly think a tsunami is a single wave, some return to the beach after the first wave hits, Lopes said. On March 11, 2011, a man in Klamath River, Calif. , died after he was swept away by a second wave while taking pictures of the Japan tsunami, Lopes said.
Tsunamis race across the deep ocean at jet speed, some 500 mph (800 km/h). Near shore, the killer waves slow to between 10 to 20 mph (16 to 32 km/h) and gain height. If the offshore slope is gentle and gradual, the tsunami will likely come in looking like a rapidly approaching tide.
If the transition from deep ocean to shoreline is steep and cliff-like, then the wave will resemble a movie-like specter, arriving as an onrushing wall of water. [Waves of Destruction: History’s Biggest Tsunamis]Look and listen for warning signsEither way, standing at the beach, at sea level, means losing perspective.
«It’s a matter of optical illusion and how fast your eye interprets the speed of moving water,» Lopes said. «People just can’t estimate the speed of the wave, and [so they] get themselves in trouble. «Linger too long and you may run out of time to find somewhere safe.
«If they’re on the beach, there’s no way in heck they’re going to outrun it,» said Nathan Wood, a tsunami modeler with the U. Geological Survey in Portland, Ore. «Technically, if you’re 10 blocks in, and the waves are full of debris [and slowing from friction], there’s a chance, but for most people that’s not realistic,» he said.
So if the beach starts shaking or the ocean looks or sounds strange, head for the highest elevation around immediately. «Sometimes the only warning you may get are these environmental clues,» Lopes said.
«These are the indicators that you are in serious danger. «High ground is best in situations like these; steel-reinforced concrete buildings or parking structures work in a pinch, but even climbing trees will help if nothing else is available. Some people who sought refuge in trees survived the 1960 Chile tsunami, though others were torn from their branches.
Why people put themselves at riskAnother fatal mistake people make when fleeing from tsunamis is underestimating how far the water can travel inland, Lopes said. In this graphic video of the 2011 Japan tsunami, shot from a hillside, residents fleeing the tsunami are nearly caught by the powerful wave even after it had already destroyed half the town.
ALOOP Expert Panel – How fast do tsunami travel, and how far inland do they go?
Tsunamis can travel as far as 10 miles (16 km) inland, depending on the shape and slope of the shoreline. Hurricanes also drive the sea miles inward, putting people at risk. But even hurricane veterans may ignore orders to evacuate. As with tsunamis, a lack of understanding lays at the heart of this willingness to risk everything, according to studies by NOAA. Storm surge floods a section of Coast Guard Station New York, located on Staten Island, as Hurricane Sandy approaches New York Harbor, Monday, Oct. 29, 2012. (Image credit: U. Coast Guard photo by Petty Officer 2nd Class Erik Swanson. )Hurricane evacuation orders are due to dangers from storm surges, not wind, Rhome explained. «People are enamored with the wind, but it’s storm surge that has the greatest potential to take life,» he said.
- «We’ve consulted with social scientists and communications experts, and the number one reason why people stay is that they don’t understand storm surge,» said Jaime Rhome, storm surge team leader at the National Hurricane Center in Miami
«The majority of deaths occurring in hurricanes are from drowning, not wind. «Storm surge is the force of hurricane winds driving the ocean landward, which raises sea level. The water penetrates miles inland. Waves kicked up by the hurricane travel on top of the storm surge, pounding everything in their path.
People who go out in the surge — residents who wait too long to evacuate, for example — may find themselves knocked off their feet and swept away. «People have a hard time imagining seawater can come that far inland,» Rhome said.
«They can’t envision the ocean can rise that high or be that violent. «Editor’s note: This story was updated to reflect the March 11, 2011, U. tsunami death was at Klamath River, Calif. , not Crescent City, Calif. Email Becky Oskin or follow her @beckyoskin.
Follow us @livescience, Facebook & Google+. Original article on LiveScience. com. Becky Oskin covers Earth science, climate change and space, as well as general science topics. Becky was a science reporter at Live Science and The Pasadena Star-News; she has freelanced for New Scientist and the American Institute of Physics.
She earned a master’s degree in geology from Caltech, a bachelor’s degree from Washington State University, and a graduate certificate in science writing from the University of California, Santa Cruz..
Can a tsunami travel 3000 miles?
The Indian Ocean tsunami generated by the most powerful earthquake in decades on December 26 is believed to have killed more than 150,000 people and made millions homeless, making it perhaps the most destructive tsunami in history. The epicenter of the 9.
0 magnitude quake was under the Indian Ocean near the west coast of the Indonesian island of Sumatra, according to the U. Geological Survey, which monitors earthquakes worldwide. A violent movement of the Earth’s tectonic plates displaced an enormous amount of water, sending powerful shock waves in every direction.
Within hours killer waves radiating from the epicenter slammed into the coastline of 11 Indian Ocean countries, snatching people out to sea, drowning others in their homes or on beaches, and demolishing property from Africa to Thailand. Tsunamis have been relatively rare in the Indian Ocean.
They are most prevalent in the Pacific. But every ocean has generated the scourges. Many countries are at risk. In the wake of the Christmas weekend tsunami in the Indian Ocean, one of the worst disasters in history, National Geographic News examines the killer waves’ causes and warning signs—information that can be a lifesaver in a tsunami zone.
• A tsunami is a series of great sea waves caused by an underwater earthquake, landslide, or volcanic eruption. More rarely, a tsunami can be generated by a giant meteor impact with the ocean. Scientists have found traces of an asteroid-collision event that they say would have created a giant tsunami that swept around the Earth several times, inundating everything except the mountains 3.
5 billion years ago. The coastline of the continents was changed drastically and almost all life on land was exterminated. (Read the story)• Tsunami (pronounced soo-NAH-mee) is a Japanese word. Tsunamis are fairly common in Japan and many thousands of Japanese have been killed by them in recent centuries.
• An earthquake generates a tsunami if it is of sufficient force and there is violent movement of the earth causing substantial and sudden displacement of a massive amount of water. • A tsunami is not a single wave but a series of waves, also known as a wave train.
The first wave in a tsunami is not necessarily the most destructive. Tsunamis are not tidal waves. • Tsunami waves can be very long (as much as 60 miles, or 100 kilometers) and be as far as one hour apart.
They are able to cross entire oceans without great loss of energy. The Indian Ocean tsunami traveled as much as 3,000 miles (nearly 5,000 kilometers) to Africa, arriving with sufficient force to kill people and destroy property. Scientists say that a great earthquake of magnitude 9 struck the Pacific Northwest in 1700, and created a tsunami that caused flooding and damage on the Pacific coast of Japan.
How far inland can a 100 ft tsunami go?
Know the tsunami is coming — Most tsunamis are triggered when earthquakes near the seafloor displace a large amount of water. That water gets pushed out as a series of waves that move outwards in all directions. Undersea volcanic eruptions, landslides, and even meteorites can also spark tsunamis.
- Out on the sea, these waves can be hundreds of miles long but no taller than a few feet and travel at the speed of a jet plane, up to 500 miles per hour
- When the waves approach land, they will slow to about 20 or 30 miles an hour and begin to grow in height
Most tsunamis are less than 10 feet high when they hit land, but they can reach more than 100 feet high. When a tsunami comes ashore, areas less than 25 feet above sea level and within a mile of the sea will be in the greatest danger. However, tsunamis can surge up to 10 miles inland.
- «It’s really just kind of relentless, the water just keeps on coming and coming and coming for a long time,» Garrison-Laney says
- The tsunami could resemble a wall of water or, more likely, a rapidly rising flood
«It’s not going to look like big, curling waves like you see at the beach,» Garrison-Laney says. «It’s really a very turbulent flow that is rising and flowing onto land pretty quickly. » Before this happens, though, there may be a few warning signs. First you’ll need to survive the earthquake, if there was one.
After a strong coastal quake, make sure you get to high ground even if an official tsunami warning has not yet been issued. If a local tsunami has been generated it could be mere minutes away. «You cannot wait for the authorities if it’s a significant earthquake and you live along the coast,» says Denis Chang Seng, technical secretary for UNESCO’s Intergovernmental Coordination Group for the Tsunami Early Warning and Mitigation System in the North-eastern Atlantic, the Mediterranean, and connected seas.
As Denis García discovered in 1960, a tsunami can also cause the ocean to withdraw before it arrives, leaving sand and reefs bare. There may be a roaring noise like a train or jet plane as well. «You have to recognize the warning signs from nature itself,» Chang Seng says.
- Meanwhile, tsunami tracking centers such as the Pacific Tsunami Warning Center in Hawaii or the National Tsunami Warning Center in Alaska will put out an alert
- So be on the lookout for official warnings, sirens, and directions from your local authorities
«You don’t want to hesitate if you know a warning’s been issued or you’ve felt the ground shaking,» says Laura Kong, director of the International Tsunami Information Center in Honolulu. «You want to get going.
How far did the 2004 tsunami travel?
The Indian Ocean tsunami traveled as far as 3,000 miles to Africa and still arrived with sufficient force to kill people and destroy property. Many people in Indonesia reported that they saw animals fleeing for high ground minutes before the tsunami arrived – very few animal bodies were found afterward.
Can tsunamis travel up to 500 mph?
Tsunami movement — Once a tsunami forms, its speed depends on the depth of the ocean. In the deep ocean, a tsunami can move as fast as a jet plane, over 500 mph, and its wavelength, the distance from crest to crest, may be hundreds of miles. Mariners at sea will not normally notice a tsunami as it passes beneath them; in deep water, the top of the wave rarely reaches more than three feet higher than the ocean swell. On the afternoon of April 13, 2018, a large wave of water surged across Lake Michigan and flooded the shores of the picturesque beach town of Ludington, Michigan, damaging homes and boat docks, and flooding intake pipes. Thanks to a local citizen’s photos and other data, NOAA scientists reconstructed the event in models and determined this was the first ever documented meteotsunami in the Great Lakes caused by an atmospheric inertia-gravity wave.
Can you outrun a tsunami in a car?
And NO, YOU CAN’T OUTRUN A TSUNAMI. — MAYBE the world’s fastest runners could run 5-minute miles for 5 miles while a terrifying wall of water chases the athlete off the Spit. But most people couldn’t. It’s just not possible. It doesn’t really matter how fast the wave is coming in, the point is that once you get a sign of a possible tsunami, you really shouldn’t be near the wave in the first place.
Know the warning signals. Don’t ignore them or underestimate the speed of the wave. If the beach starts shaking or the ocean looks or sounds strange, head off the Spit, away from beaches and from Beluga Slough toward highest elevation immediately.
Getting to high ground is the only way to survive the monster waves. Linger too long and you may run out of time to find somewhere safe. Tsunamis can also come in as a series of inundating waves. The second wave of water is often much larger than the first. .
Is a mega tsunami possible?
There have been megatsunamis in the past, and future megatsunamis are possible but current geological consensus is that these are only local. A megatsunami in the Canary Islands would diminish to a normal tsunami by the time it reached the continents.
Can you survive a tsunami with a life jacket?
Discussion — A typical tsunami has a very high speed of roughly 700 km/h as it emerges from the deep sea, after which it suddenly slows down when it reaches shallow coastal regions where it may retain a relatively high speed of about 40 km/h. At these moments, tsunami waves rear up precipitously and one can realize the Japanese meaning of the word «tsunami» (wave «nami» in a harbor «tsu»).
This is when people witness giant surges; tsunami waves will often overcome a majority of witnesses, even if they run away to save their lives. In addition, when a tsunami recedes, the water will sweep away victims and debris from the land to the sea .
As recommended by the Japanese Sanriku coast’s old adage «Tsunami tendenko» («Run uphill on your own will when a tsunami comes»), the first defensive action against any tsunami is to act quickly and seek higher ground immediately. However, since a highly reliable tsunami detection and warning system is still in the developmental stages, people are apt to delay or even ignore evacuations [20–22].
- Some of them even deliberately take the opposite direction and head towards the beach to watch the incoming tsunami 
- Findings from the systematic literature review indicate that the primary cause of tsunami-related mortality is drowning 
During the 2004 Sumatra-Andaman Earthquake, the main cause of death was drowning due to the tsunami [25–27]. According to the Japanese National Police Agency’s report based on data obtained from post-mortem certificates after the Tohoku-Pacific Earthquake, the cause of death for 14,308 of the 15,786 fatalities (90.
64%) was drowning, while 667 (4. 23%) died from severe impact injuries . People might be crushed to death by various debris such as that from destroyed houses and buildings, wrecked boats, and cars, which would be whirling in the water, or they might be crushed against a wharf or breakwater and suffer fatal injuries.
Even so, we have to admit that large numbers of people were engulfed in the tsunami waves and drowned in the Tohoku-Pacific Earthquake on March 11, 2011. Therefore, there is an urgent need to find a technique that can prevent drowning. With such a technique, it would be possible to reduce the number of victims who drown and die in tsunamis.
- Unfortunately, however, there is a lack of information on the cause of drowning during tsunami disasters
- During the Tohoku-Pacific Earthquake, the body of every victim of the tsunami was examined by a forensic doctor or a medical coroner, and through this examination, it was confirmed that the cause of death of almost all the victims was drowning
However, there were no detailed descriptions beyond drowning in the post-mortem certificates. Why could the tsunami victims not swim? Why were they not able to cling firmly to floating objects on the surface of water? We searched the literature and could not find answers to these important questions.
- Hence, we conducted a series of experiments to analyze the cause of drowning during a tsunami
- In our experiments, all the heads of dummies not wearing PFDs were entrapped in vortices after the tsunami wave hit them
They continued whirling intensively up and down in the water but never came up to the water surface. When tsunamis engulf people below the water surface, and the rate as well as the depth of their breathing increase dramatically, people have no other choice but to inhale water since it would be nearly impossible to swim up to the water surface.
This will greatly increase the risk of drowning. Since tsunamis, whose wavelengths are very long, are generated by the displacement of huge volumes of water, the whirlpools created by them are extremely powerful and continue for a long time.
Therefore, once people without PFDs are caught up in a tsunami, it is very difficult for them to escape from such whirlpools. Even skilled swimmers without PFDs would not be able to resurface quickly and remain afloat. This severe whirling of tsunami waves is likely one of the main factors that cause the overwhelming majority of tsunami victims to drown.
The buoyancy of widely popular PFDs is 7. 031 kg (15. 5 lbs) , and the effectiveness of PFDs has been studied for recreational swimming and fishing [30–32]. However, to the best of the authors’ knowledge, there is a lack of information on the effectiveness of PFDs during catastrophic tsunami disasters.
In our experiments that employed widely popular PFDs, the dummies wearing the PFDs were not dragged underwater. They remained afloat and the heads were higher than the water level. As our experiments demonstrated, it can be concluded that when people are engulfed within tsunami waves, PFDs will provide them with a higher chance of survival because they will remain on the surface of tsunami waves and are still able to breathe.
In other words, a PFD is a critical piece of equipment for surviving tsunamis. In critical situations, when a tsunami wave is already visible to people and there are no PFDs around, they might be able to put empty plastic bottles between their skin and clothing, hold on to garbage cans, or wear helmets as substitutions for PFDs and other protective gear.
These actions represent the second-best tsunami survival technique. It is reasonable to assume that hypothermia victims were included in the 15,786 fatalities (90. 64%) of the Tohoku-Pacific Earthquake because the seawater temperature was very low (5 to 7°C) .
If the entire human body is immersed in water at such low temperatures, its core temperature will decrease to a critical level within 2 h . People with PFDs might be transported extensively far from the coast; therefore, it will be necessary to establish a reliable rescue system to save them before their core temperature drops to a severe level where hypothermia can set in.
People lose consciousness when their core temperature drops to 30°C. However, if people wear PFDs, they would be able to avoid drowning even if they lose consciousness as they would merely float on the water surface while still retaining their ability to breathe [34–36].
- Tsunamis might kill people in multiple ways as mentioned above
- In the next series of experiments, we plan on evaluating whether a dummy wearing a PFD would be able to overcome a crash with debris swept by the water or a crash against a concrete block
Notably, the wave heights of our artificial tsunamis were much lower than those of natural tsunamis, which often exceed 10 m. Regardless, our experiments demonstrated that dummies without PFDs were caught up in the vortex and could not resurface after they were hit by the artificial tsunami.
- On the other hand, dummies wearing PFDs were not drawn under and were able to continue to float on the water surface
- Based on these results, we are planning to carry out further experiments with a 1
- 5 m high artificial tsunami and simulations of 10 m high tsunami waves using computer software [37,38]
The results of our series of experiments are important as a first step to improve survivorship during tsunami disasters, and application of the results could likely save numerous lives.
Can you surf a tsunami?
Asked by: Kevin Scott, EdinburghDefinitely not. A tsunami is nothing like a regular wave; it isn’t a surface phenomenon generated by the wind, it is a displacement of the entire water column as a result of an undersea earthquake. A tsunami does not have a clean, surfable face, it is just a roiling mass of white water full of rocks and coral.
What is the biggest tsunami ever recorded?
The tallest tsunami ever recorded occurred after the Lituya Bay earthquake with a reported height of 524 m (1,720 ft). A total of 5 people were killed during the tsunami, which left many people injured and many homes destroyed.
Can dogs sense tsunami?
What Sri Lanka’s animals knew that humans didn’t. — Reports from Sri Lanka after Sunday’s tsunami say that despite the enormous number of human casualties—116,000 deaths and rising, at last count—many animals seem to have survived the tidal wave unscathed.
At Sri Lanka’s national wildlife park at Yala, which houses elephants, buffalo, monkeys, and wild cats, no animal corpses were found on Wednesday. (Yet according to Reuters, the human devastation there was as tragic as elsewhere: Only 30 of the 250 tourist vehicles that entered the park on Sunday returned to base.
) Did Yala’s animals sense the oncoming tsunami and flee to safety? There’s a good chance the wildlife knew trouble was on the way. History is littered with tales about animals acting weirdly before natural disasters, but the phenomenon has been hard for scientists to pin down.
- Sometimes animals get crazy before a quake, sometimes they don’t
- Here’s what we know: Animals have sensory abilities different from our own, and they might have tipped them off to Sunday’s disaster
- First, it’s possible that the animals may have heard the quake before the tsunami hit land
The underwater rupture likely generated sound waves known as infrasound or infrasonic sound. These low tones can be created by hugely energetic events, like meteor strikes, volcanic eruptions, avalanches, and earthquakes. Humans can’t hear infrasound—the lowest key on a piano is about the lowest tone the human ear can detect.
- But many animals—dogs, elephants, giraffes, hippos, tigers, pigeons, even cassowaries—can hear infrasound waves
- A second early-warning sign the animals might have sensed is ground vibration
- In addition to spawning the tsunamis, Sunday’s quake generated massive vibrational waves that spread out from the epicenter on the floor of the Indian Ocean’s Bay of Bengal and traveled through the surface of the Earth
Known as Rayleigh waves (for Lord Rayleigh, who predicted their existence in 1885), these vibrations move through the ground like waves move on the surface of the ocean. They travel at 10 times the speed of sound. The waves would have reached Sri Lanka hours before the water hit.
- Mammals, birds, insects, and spiders can detect Rayleigh waves
- Most can feel the movement in their bodies, although some, like snakes and salamanders, put their ears to the ground in order to perceive it
The animals at Yala might have felt the Rayleigh waves and run for higher ground. Why would they instinctively flee to higher ground—the safest place to be in the event of a tsunami? Typically, animals scatter away from a place where they are disturbed.
- So, in this case, «away» may have meant away from the sea, and incidentally, away from sea level
- Or maybe it’s not as accidental as all that
- It’s easy to imagine that one of evolution’s general lessons is: If the ground beneath your feet starts moving, move up and away as fast as you can
What about humans—where were our red flags? Humans feel infrasound. But we don’t necessarily know that that’s what we’re feeling. Some people experience sensations of being spooked or even feeling religious in the presence of infrasound. We also experience Rayleigh waves via special sensors in our joints (called pacinian corpuscles), which exist just for that purpose.
Sadly, it seems we don’t pay attention to the information when we get it. Maybe we screen it out because there’s so much going on before our eyes and in our ears. Humans have a lot of things on their minds, and usually that works out OK.
Next question? Explainer thanks Dr. Alfred J. Bedard Jr. at the NOAA/Environmental Technology Laboratory and Dr. Peggy Hill at the University of Tulsa, Okla..
What was the worst tsunami ever?
What is the worst tsunami in history? — What has commonly been considered the worst tsunami in history occurred in the Indian Ocean in 2004. It was the result of a 9. 1 magnitude earthquake that occurred off the coast of Sumatra in Indonesia. It caused a wave that was a record-breaking 164 feet tall, resulting in around $10 billion in damage and the deaths of 230,000 people.
Can you survive a tsunami underwater?
A Ruthless Wave Train If a vessel is hit by a tsunami near shore in shallow water, it will be shattered to pieces. Tsunamis can also be brutal to all sorts of life forms underwater. A diver, for instance, will hardly survive a tsunami because he will be caught by violent spinning currents.
How tall is the biggest tsunami?
What was the highest tsunami? The highest, reliably measured tsunami on record occurred in Lituya Bay, Alaska. This unusual event was caused by a massive landslide that fell into the bay on July 9, 1958. The resulting wave surged up the slope on the opposite side of the narrow bay to a height of 518 m(1,700 ft).
Some scientists believe that even higher tsunamis have occurred a long time ago when asteroids, or large meteors, fell into the ocean. Two areas where studies are underway to look for evidence of such tsunamis are Hawaii and the coast of the Gulf of Mexico.
Usually, a tsunami is generated when an offshore earthquake moves the ocean bottom in the vertical direction. The waves then propagate towards the coast, growing larger as the water becomes more shallow. Measurements in the last 10 years have documented a 32 m maximum wave height in Okushiri, Japan, and 26 m height on Flores Island Indonesia.
- These were exceptionally high values due to topographic and bathymetric situations that were somewhat special
- More typically, the heights of 10 destructive tsunamis in the Pacific since 1990 ranged from about 3 to 15 m; these claimed more than 4000 lives
If you want to explore the issue in more detail, I invite you to visit NOAA’s National Geophysical Data Center site. The site offers a historical tsunami database that can be searched on-line. Authority: NOAA Center for Tsunami ResearchAre tsunamis more (or less) dangerous on islands or on normal coasts? Is Hawaii hit so often because it’s an island or because it’s «in the way» of most tsunamis in the Pacific? I read somewhere that the most dangerous tsunamis for Hawaii are those generated by local earthquakes (on the islands itself).
I don’t understand: wouldn’t the tsunami flee the island if it’s generated by it? The article seemed to suggest that an earthquake under one of the islands implied a violent tsunami on hawaiian beaches shortly after.
Because Hawaii is in the middle of the North Pacific and because this ocean is surrounded by a many earthquake/tsunami generating regions, Hawaii tends to receive many trans-oceanic tsunamis. Also, volcanic islands tend to have steep, unstable slopes where landslides can occur.
- The southeastern coast of the Island of Hawaii (with active volcanoes and ground movement) has had two major landslides in the past 150 years that have generated dangerous tsunamis
- While most of the tsunami energy does radiate out to sea, some remains near the coast
There are two reasons for this. The first is that tsunami waves tend to turn toward shallow water and can be trapped near the coast in the form of ‘edge waves’; these can propagate right around an island. The second is the reflection of tsunami waves that occurs when the wave encounter the sharp change in water depth between the shallow areas just off the coast and the deep ocean water farther away from the island.
- The reason that the landslide tsunamis reach the beach so quickly is that they have only a short distance to propagate away from the landslide area before they reach the beach
- Authority: Dr
- Frank Gonzalez, interviews in 1998, NOAA Center for Tsunami ResearchWhy are tsunamis so dangerous? Tsunamis cause the water level and currents to rise rapidly, sometimes high enough to drown or injury people who have not escaped away from the shore to high ground
Dangerous waves can follow the first tsunami wave, trapping people who returned to the danger area because they thought the tsunami was over. Also, people can be caught unaware if they don’t know the natural tsunami signs (earthquake shaking, water receding rapidly from the beach, a loud noise like a freight train coming from the ocean) or they are places where there are no tsunami warning systems.
Strong tsunamis damage ports and harbors, as well as tourist areas, thereby damaging relief efforts and the economy of the communities. Authority: Dr. Hal Mofjeld, interview in February 25, 2005, NOAA Center for Tsunami ResearchHow does ocean bottom pressure affect sea surface height? To answer your question, all DART II systems consist of a sea surface buoy and a companion seafloor bottom pressure recorder (BPR) unit typically sited within 2km of one another.
The BPR takes and records measurements of the overlying water column as pressure in units of absolute pounds per square inch [psia] and telemeters these measurements through the water column to the surface buoy whose sole function is communication both to and from land stations via satellite.
All DART II BPRs measure pressure (and temperature) as frequency counts. A quartz crystal enclosed in an evacuated chamber and linked to seawater near the ocean floor by an oil filled tube oscillates as a function of the pressure exerted on it, the pressure of the overlying water column.
Electronics and precise base crystal and timing clocks measure the pressure as an integration over 15-second intervals continuously for the entire time a BPR is deployed. These measurements and temperature measurements made the same way (oscillating quartz crystal integrated over 15-second intervals) are recorded in the unit as frequency counts.
When a BPR detects an earthquake or tsunami, measurements are immediately sent to the surface buoy for telemetry to shore and continue to be sent on a regular but rapid reporting schedule. It is these measurements that are converted to depth in meters by algorithms controlling BPR measurements, processing, and storage.
The precise conversion of measured pressure considers temperature, latitude, water density, and gravitational variation. Because gravitational potential and density are typically small terms, and because we are interested in rapid notification of threat based on relative sea level, the algorithms in DART II technology convert pressure to depth using a constant that assumes ‘standard’ seawater (Temperature = 0ºC, Salinity = 35 PPT (Parts per thousand)).
Specifically, water depth [meters] sent to shore by the surface buoy is the result of correcting measured pressure [psia] for temperature and applying a constant 670mm/psia conversion factor. Here are two references in case you are interested in reading further: 1.
Saunders P. , Fofonoff N. (1976): Conversion of pressure to depth in the ocean. Deep Sea Research 23:109-111. http://www. paroscientific. com/pdf/ptodepth. pdf Authority: Marie Eble, NOAA Center for Tsunami Research.
How long can a tsunami last?
Tsunami Safety — 6. 1 Why are tsunamis dangerous? 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
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 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:
If you have children in school in a tsunami hazard zone, find out the school’s plans for evacuating and keeping children safe. If you are visiting the coast, find out about local tsunami safety. Your hotel or campground should have this information. Visit the NWS Tsunami Safety and International Tsunami Information Center websites to learn more. 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.
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 (i. , official or natural). 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:
If you are in a tsunami hazard zone and receive a natural tsunami warning, a tsunami could arrive within minutes:
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.
tsunami maps). Both are equally important. You may not get both. 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.
In the United States, to find out if you are in a tsunami hazard zone, visit the Tsunami Maps web page. Visit the NWS Tsunami Safety and International Tsunami Information Center websites to learn more. 5 Who issues tsunami evacuation orders? For all U. states and territories, evacuation requests/instructions are typically issued and coordinated by local emergency management officials.
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.
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 (e. , reinforced concrete) and tall buildings may be able to provide protection if no other options are available.
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.
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 you get a tsunami warning, your response will depend largely on where you are. In the United States, in general, it is recommended that:
*Safe depths vary by region, but the minimum safe depth is 30 fathoms (180 feet). 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:
If you have a question regarding tsunamis we would like to hear from you.