A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake.

Earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

volcanic eruption Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often ...

s and other

underwater explosion An underwater explosion (also known as an UNDEX) is a chemical or nuclear explosion that occurs under the surface of a body of water. While useful in anti-ship and submarine warfare, underwater bombs are not as effective against coastal facilities. ...

s (including detonations, landslides, glacier calvings, meteorite impacts and other disturbances) above or below water all have the potential to generate a tsunami. Unlike normal ocean waves, which are generated by wind, or

tide Tides are the rise and fall of sea levels caused by the combined effects of the gravity, gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide t ...

s, which are in turn generated by the gravitational pull of the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

and the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

, a tsunami is generated by the displacement of water from a large event. Tsunami waves do not resemble normal undersea currents or

sea waves In fluid dynamics, a wind wave, water wave, or wind-generated water wave, is a surface wave that occurs on the free surface of bodies of water as a result from the wind blowing over the water surface. The contact distance in the direction of t ...

because their

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...

is far longer. Rather than appearing as a

breaking wave In fluid dynamics, a breaking wave or breaker is a wave whose amplitude reaches a critical level at which large amounts of wave energy transform into Wave turbulence, turbulent kinetic energy. At this point, simple physical models that describ ...

, a tsunami may instead initially resemble a rapidly rising

. For this reason, it is often referred to as a tidal wave, although this usage is not favoured by the scientific community because it might give the false impression of a causal relationship between tides and tsunamis. Tsunamis generally consist of a series of waves, with

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

s ranging from minutes to hours, arriving in a so-called "

wave train In physics, a wave packet (or wave train) is a short "burst" or "envelope" of localized wave action that travels as a unit. A wave packet can be analyzed into, or can be synthesized from, an infinite set of component sinusoidal waves of diffe ...

". Wave heights of tens of metres can be generated by large events. Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous, and they can affect entire ocean basins. The

2004 Indian Ocean tsunami An earthquake and a tsunami, known as the Boxing Day Tsunami and, by the scientific community, the Sumatra–Andaman earthquake, occurred at 07:58:53 local time (UTC+7) on 26 December 2004, with an epicentre off the west coast of northern Suma ...

was among the deadliest natural disasters in human history, with at least 230,000 people killed or missing in 14 countries bordering the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...

. The

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

historian

Thucydides Thucydides (; grc, , }; BC) was an Athenian historian and general. His ''History of the Peloponnesian War'' recounts the fifth-century BC war between Sparta and Athens until the year 411 BC. Thucydides has been dubbed the father of "scientifi ...

suggested in his 5th century BC ''

History of the Peloponnesian War The ''History of the Peloponnesian War'' is a historical account of the Peloponnesian War (431–404 BC), which was fought between the Peloponnesian League (led by Sparta) and the Delian League (led by Athens). It was written by Thucydides, an ...

'' that tsunamis were related to

submarine earthquake A submarine, undersea, or underwater earthquake is an earthquake that occurs underwater at the bottom of a body of water, especially an ocean. They are the leading cause of tsunamis. The magnitude can be measured scientifically by the use of the ...

s, but the understanding of tsunamis remained slim until the 20th century, and much remains unknown. Major areas of current research include determining why some large earthquakes do not generate tsunamis while other smaller ones do. This ongoing research is designed to help accurately forecast the passage of tsunamis across oceans as well as how tsunami waves interact with shorelines.

Terminology

Tsunami

The term "tsunami" is a borrowing from the Japanese ''tsunami'' , meaning "harbour wave." For the plural, one can either follow ordinary English practice and add an ''s'', or use an invariable plural as in the Japanese. Some English speakers alter the word's initial to an by dropping the "t," since English does not natively permit /ts/ at the beginning of words, though the original Japanese pronunciation is .

Tidal wave

Tsunamis are sometimes referred to as ''tidal waves''. This once-popular term derives from the most common appearance of a tsunami, which is that of an extraordinarily high

tidal bore Tidal is the adjectival form of tide. Tidal may also refer to: * ''Tidal'' (album), a 1996 album by Fiona Apple * Tidal (king), a king involved in the Battle of the Vale of Siddim * TidalCycles, a live coding environment for music * Tidal (servic ...

. Tsunamis and tides both produce waves of water that move inland, but in the case of a tsunami, the inland movement of water may be much greater, giving the impression of an incredibly high and forceful tide. In recent years, the term "tidal wave" has fallen out of favour, especially in the scientific community, because the causes of tsunamis have nothing to do with those of

s, which are produced by the gravitational pull of the moon and sun rather than the displacement of water. Although the meanings of "tidal" include "resembling" or "having the form or character of" tides, use of the term ''tidal wave'' is discouraged by geologists and oceanographers. A 1969 episode of the TV crime show ''

Hawaii Five-O Hawaii Five-O or Hawaii Five-0 may refer to: * ''Hawaii Five-0'' (2010 TV series), an American action police procedural television series * ''Hawaii Five-O'' (1968 TV series), an American police procedural drama series produced by CBS Productio ...

'' entitled "Forty Feet High and It Kills!" used the terms "tsunami" and "tidal wave" interchangeably.

Seismic sea wave

The term ''seismic sea wave'' is also used to refer to the phenomenon because the waves most often are generated by

seismic Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...

activity such as earthquakes. Prior to the rise of the use of the term ''tsunami'' in English, scientists generally encouraged the use of the term ''seismic sea wave'' rather than ''tidal wave''. However, like ''tsunami'', ''seismic sea wave'' is not a completely accurate term, as forces other than earthquakes—including underwater

landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...

s, volcanic eruptions, underwater explosions, land or ice

slumping Slumping is a technique in which items are made in a kiln by means of shaping glass over molds at high temperatures. The slumping of a pyrometric cone is often used to measure temperature in a kiln. Technique Slumping glass is a highly techni ...

into the ocean,

meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...

impacts, and the weather when the atmospheric pressure changes very rapidly—can generate such waves by displacing water.

History

While Japan may have the longest

recorded history Recorded history or written history describes the historical events that have been recorded in a written form or other documented communication which are subsequently evaluated by historians using the historical method. For broader world hist ...

of tsunamis, the sheer destruction caused by the

2004 Indian Ocean earthquake and tsunami An earthquake and a tsunami, known as the Boxing Day Tsunami and, by the scientific community, the Sumatra–Andaman earthquake, occurred at 07:58:53 local time (UTC+7) on 26 December 2004, with an epicentre off the west coast of northern Suma ...

event mark it as the most devastating of its kind in modern times, killing around 230,000 people. The Sumatran region is also accustomed to tsunamis, with earthquakes of varying magnitudes regularly occurring off the coast of the island. Tsunamis are an often underestimated hazard in the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

and parts of Europe. Of historical and current (with regard to risk assumptions) importance are the 1755 Lisbon earthquake and tsunami (which was caused by the

Azores–Gibraltar Transform Fault The Azores–Gibraltar Transform Fault (AGFZ), also called a fault zone and a fracture zone, is a major seismic zone in the Eastern Atlantic Ocean between the Azores and the Strait of Gibraltar. It is the product of the complex interaction between ...

), the

1783 Calabrian earthquakes The 1783 Calabrian earthquakes were a sequence of five strong earthquakes that hit the region of Calabria in southern Italy (then part of the Kingdom of Naples), the first two of which produced significant tsunamis. The epicenters form a clear a ...

, each causing several tens of thousands of deaths and the

1908 Messina earthquake The 1908 Messina earthquake (also known as the 1908 Messina and Reggio earthquake) occurred on 28 December in Sicily and Calabria, southern Italy with a moment magnitude of 7.1 and a maximum Mercalli intensity of XI (''Extreme''). The epicen ...

and tsunami. The tsunami claimed more than 123,000 lives in Sicily and Calabria and is among the most deadly natural disasters in modern Europe. The

Storegga Slide The three Storegga Slides ( no, Storeggaraset) are amongst the largest known submarine landslides. They occurred at the edge of Norway's continental shelf in the Norwegian Sea, approximately 6225–6170 BCE. The collapse involved an estimated ...

in the Norwegian Sea and some examples of

tsunamis affecting the British Isles Tsunamis affecting the British Isles are extremely uncommon, and there have only been two confirmed cases in recorded history. Meteotsunamis (displacements due to atmospheric pressure, rather than seismic shock) are somewhat more common, especially ...

refer to landslide and

meteotsunami A meteotsunami or meteorological tsunamiTsunami Glossary 2008
, UNESCO is a

As early as 426 BC the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

historian

inquired in his book ''

'' about the causes of tsunami, and was the first to argue that ocean earthquakes must be the cause.

“A History of the Peloponnesian War”, 3.89.1–4
/ref> The oldest human record of a tsunami dates back to

479 BC __NOTOC__ Year 479 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Vibulanus and Rutilus (or, less frequently, year 275 ''Ab urbe condita''). The denomination 479 BC for this year has ...

, in the Greek colony of

Potidaea __NOTOC__ Potidaea (; grc, Ποτίδαια, ''Potidaia'', also Ποτείδαια, ''Poteidaia'') was a colony founded by the Corinthians around 600 BC in the narrowest point of the peninsula of Pallene, the westernmost of three peninsulas at ...

, thought to be triggered by an earthquake. The tsunami may have saved the colony from an invasion by the

Achaemenid Empire The Achaemenid Empire or Achaemenian Empire (; peo, 𐎧𐏁𐏂, , ), also called the First Persian Empire, was an ancient Iranian empire founded by Cyrus the Great in 550 BC. Based in Western Asia, it was contemporarily the largest em ...

The cause, in my opinion, of this phenomenon must be sought in the earthquake. At the point where its shock has been the most violent the sea is driven back, and suddenly recoiling with redoubled force, causes the inundation. Without an earthquake I do not see how such an accident could happen.
Thucydides Thucydides (; grc, , }; BC) was an Athenian historian and general. His ''History of the Peloponnesian War'' recounts the fifth-century BC war between Sparta and Athens until the year 411 BC. Thucydides has been dubbed the father of "scientifi ...

“A History of the Peloponnesian War”, 3.89.5
/ref>

The

Roman Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a letter ...

historian

Ammianus Marcellinus Ammianus Marcellinus (occasionally Anglicisation, anglicised as Ammian) (born , died 400) was a Roman soldier and historian who wrote the penultimate major historical account surviving from Ancient history, antiquity (preceding Procopius). His w ...

(''Res Gestae'' 26.10.15–19) described the typical sequence of a tsunami, including an incipient earthquake, the sudden retreat of the sea and a following gigantic wave, after the 365 AD tsunami devastated

Alexandria Alexandria ( or ; ar, ٱلْإِسْكَنْدَرِيَّةُ ; grc-gre, Αλεξάνδρεια, Alexándria) is the second largest city in Egypt, and the largest city on the Mediterranean coast. Founded in by Alexander the Great, Alexandria ...

.Stanley, Jean-Daniel & Jorstad, Thomas F. (2005),
The 365 A.D. Tsunami Destruction of Alexandria, Egypt: Erosion, Deformation of Strata and Introduction of Allochthonous Material
"

Causes

The principal generation mechanism of a tsunami is the displacement of a substantial volume of water or perturbation of the sea. This displacement of water is usually caused by earthquakes, but can also be attributed to landslides, volcanic eruptions, glacier calvings or more rarely by meteorites and nuclear tests. However, the possibility of a meteorite causing a tsunami is debated.

Seismicity

Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the Earth's crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. More specifically, a tsunami can be generated when

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If ...

s associated with convergent or destructive

plate boundaries Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...

move abruptly, resulting in water displacement, owing to the vertical component of movement involved. Movement on normal (extensional) faults can also cause displacement of the seabed, but only the largest of such events (typically related to flexure in the

outer trench swell The outer trench swell, outer trench high, or outer rise is a subtle ridge on the seafloor near an oceanic trench, where a descending plate begins to flex and fault in preparation for its descent into the mantle at a subduction zone. The lithosp ...

) cause enough displacement to give rise to a significant tsunami, such as the 1977 Sumba and 1933 Sanriku events. File:Eq-gen1.svg, Drawing of

tectonic plate boundary Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...

before

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

File:Eq-gen2.svg, Over-riding plate bulges under strain, causing

tectonic uplift Tectonic uplift is the geologic uplift of Earth's surface that is attributed to plate tectonics. While isostatic response is important, an increase in the mean elevation of a region can only occur in response to tectonic processes of crustal thick ...

. File:Eq-gen3.svg, Plate slips, causing

subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope move ...

and releasing energy into water. File:Eq-gen4.svg, The energy released produces tsunami waves. Tsunamis have a small wave height offshore, and a very long

(often hundreds of kilometres long, whereas normal ocean waves have a wavelength of only 30 or 40 metres), which is why they generally pass unnoticed at sea, forming only a slight swell usually about above the normal sea surface. They grow in height when they reach shallower water, in a

wave shoaling In fluid dynamics, wave shoaling is the effect by which surface waves, entering shallower water, change in wave height. It is caused by the fact that the group velocity, which is also the wave-energy transport velocity, changes with water depth ...

process described below. A tsunami can occur in any tidal state and even at low tide can still inundate coastal areas. On April 1, 1946, the 8.6 Aleutian Islands earthquake occurred with a maximum

Mercalli intensity The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the eff ...

of VI (''Strong''). It generated a tsunami which inundated

Hilo Hilo () is a census-designated place (CDP) and the largest settlement in Hawaii County, Hawaii, Hawaii County, Hawaii, United States, which encompasses the Hawaii (island), Island of Hawaii. The population was 44,186 according to the 2020 United ...

on the island of Hawaii with a surge. Between 165 and 173 were killed. The area where the earthquake occurred is where the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

floor is

subducting Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

(or being pushed downwards) under Alaska. Examples of tsunamis originating at locations away from convergent boundaries include

Storegga The three Storegga Slides ( no, Storeggaraset) are amongst the largest known submarine landslides. They occurred at the edge of Norway's continental shelf in the Norwegian Sea, approximately 6225–6170 BCE. The collapse involved an estimated l ...

about 8,000 years ago,

Grand Banks The Grand Banks of Newfoundland are a series of underwater plateaus south-east of the island of Newfoundland on the North American continental shelf. The Grand Banks are one of the world's richest fishing grounds, supporting Atlantic cod, swordf ...

in 1929, and

Papua New Guinea Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...

in 1998 (Tappin, 2001). The Grand Banks and Papua New Guinea tsunamis came from earthquakes which destabilised sediments, causing them to flow into the ocean and generate a tsunami. They dissipated before travelling transoceanic distances. The cause of the Storegga sediment failure is unknown. Possibilities include an overloading of the sediments, an earthquake or a release of gas hydrates (methane etc.). The

1960 Valdivia earthquake The 1960 Valdivia earthquake and tsunami ( es, link=no, Terremoto de Valdivia) or the Great Chilean earthquake (''Gran terremoto de Chile'') on 22 May 1960 was the most powerful earthquake ever recorded. Various studies have placed it at 9.4– ...

( ''M''_w 9.5),

1964 Alaska earthquake The 1964 Alaskan earthquake, also known as the Great Alaskan earthquake and Good Friday earthquake, occurred at 5:36 PM AKST on Good Friday, March 27.

(''M''_w 9.2),

2004 Indian Ocean earthquake An earthquake and a tsunami, known as the Boxing Day Tsunami and, by the scientific community, the Sumatra–Andaman earthquake, occurred at 07:58:53 local time (UTC+7) on 26 December 2004, with an epicentre off the west coast of northern Suma ...

(''M''_w 9.2), and

2011 Tōhoku earthquake Eleven or 11 may refer to: *11 (number), the natural number following 10 and preceding 12 * one of the years 11 BC, AD 11, 1911, 2011, or any year ending in 11 Literature * ''Eleven'' (novel), a 2006 novel by British author David Llewellyn *''El ...

(''M''_w9.0) are recent examples of powerful

megathrust earthquake Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthqua ...

s that generated tsunamis (known as teletsunamis) that can cross entire oceans. Smaller (''M''_w 4.2) earthquakes in Japan can trigger tsunamis (called local and regional tsunamis) that can devastate stretches of coastline, but can do so in only a few minutes at a time.

Landslides

The

Tauredunum event The Tauredunum event (german: Tauredunum-Ereignis) of 563 AD was a tsunami on Lake Geneva (then under the Frankish territory of the Kingdom of Orleans), triggered by a massive landslide which caused widespread devastation and loss of life along t ...

was a large tsunami on

Lake Geneva , image = Lake Geneva by Sentinel-2.jpg , caption = Satellite image , image_bathymetry = , caption_bathymetry = , location = Switzerland, France , coords = , lake_type = Glacial lak ...

in 563 CE, caused by sedimentary deposits destabilized by a landslide. In the 1950s, it was discovered that tsunamis larger than had previously been believed possible can be caused by giant submarine landslides. These large volumes of rapidly displaced water transfer energy at a faster rate than the water can absorb. Their existence was confirmed in 1958, when a giant landslide in

Lituya Bay Lituya Bay (; Tlingit: ''Ltu.aa'',. Spelled L'tua in translation of Tebenkov's log. meaning 'lake within the point') is a fjord located on the coast of the south-east part of the U.S. state of Alaska. It is long and wide at its widest point. ...

, Alaska, caused the highest wave ever recorded, which had a height of . The wave did not travel far as it struck land almost immediately. The wave struck three boats—each with two people aboard—anchored in the bay. One boat rode out the wave, but the wave sank the other two, killing both people aboard one of them. Another landslide-tsunami event occurred in 1963 when a massive landslide from

Monte Toc Monte Toc, nicknamed the walking mountain by locals due to its tendency to experience landslides, is a mountain on the border between Veneto and Friuli-Venezia Giulia in Northern Italy best known for the Vajont Dam, which was built at the mountai ...

entered the reservoir behind the

Vajont Dam The Vajont Dam (or Vaiont Dam) is a disused dam in northern Italy. It is one of the tallest dams in the world, with a height of . It is in the valley of the Vajont River under Monte Toc, in the municipality of Erto e Casso, north of Venice. ...

in Italy. The resulting wave surged over the -high dam by and destroyed several towns. Around 2,000 people died. Scientists named these waves

megatsunami A megatsunami is a very large wave created by a large, sudden displacement of material into a body of water. Megatsunamis have quite different features from ordinary tsunamis. Ordinary tsunamis are caused by underwater tectonic activity (movemen ...

s. Some geologists claim that large landslides from volcanic islands, e.g.

Cumbre Vieja The Cumbre Vieja (; meaning "Old Summit") is an active volcanic ridge on the island of La Palma in the Canary Islands, Spain. The spine of Cumbre Vieja trends in an approximate north–south direction, comprising the southern half of La Palma, ...

La Palma La Palma (, ), also known as ''La isla bonita'' () and officially San Miguel de La Palma, is the most north-westerly island of the Canary Islands, Spain. La Palma has an area of making it the fifth largest of the eight main Canary Islands. The ...

(

Cumbre Vieja tsunami hazard The island of La Palma in the Canary Islands is at risk of undergoing a large landslide, which could cause a tsunami in the Atlantic Ocean. Volcanic islands and volcanoes on land frequently undergo large landslides/collapses, which have been do ...

) in the

Canary Islands The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Morocc ...

, may be able to generate megatsunamis that can cross oceans, but this is disputed by many others. In general, landslides generate displacements mainly in the shallower parts of the coastline, and there is conjecture about the nature of large landslides that enter the water. This has been shown to subsequently affect water in enclosed bays and lakes, but a landslide large enough to cause a transoceanic tsunami has not occurred within recorded history. Susceptible locations are believed to be the Big Island of

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

, Fogo in the

Cape Verde Islands , national_anthem = () , official_languages = Portuguese , national_languages = Cape Verdean Creole , capital = Praia , coordinates = , largest_city = capital , demonym ...

, La Reunion in the

, and

on the island of

in the

; along with other volcanic ocean islands. This is because large masses of relatively unconsolidated volcanic material occurs on the flanks and in some cases detachment planes are believed to be developing. However, there is growing controversy about how dangerous these slopes actually are.

Volcanic eruptions

Other than by landslides or

sector collapse A sector collapse is the collapse of a portion of a volcano due to a phreatic eruption, an earthquake, or the intervention of new magma. Occurring on many volcanoes, sector collapses are generally one of the most hazardous volcanic events, and will ...

, volcanoes may be able to generate waves by

pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of bu ...

submergence, caldera collapse, or underwater explosions. Tsunamis have been triggered by a number of volcanic eruptions, including the

1883 eruption of Krakatoa The 1883 eruption of Krakatoa ( id, Letusan Krakatau 1883) in the Sunda Strait occurred from 20 May until 21 October 1883, peaking in the late morning hours of 27 August when over 70% of the island of Krakatoa and its surrounding archipelago w ...

, and the 2022 Hunga Tonga–Hunga Ha'apai eruption. Over 20% of all fatalities caused by volcanism during the past 250 years are estimated to have been caused by volcanogenic tsunamis. Debate has persisted over the origins and source mechanisms of these types of tsunamis, such as those generated by Krakatoa in 1883, and they remain lesser understood than their seismic relatives. This poses a large problem of awareness and preparedness, as exemplified by the eruption and collapse of Anak Krakatoa in 2018, which killed 426 and injured thousands when no warning was available. It is still regarded that lateral landslides and ocean-entering pyroclastic currents are most likely to generate the largest and most hazardous waves from volcanism; however, field investigation of the Tongan event, as well as developments in numerical modelling methods, currently aim to expand the understanding of the other source mechanisms.

Meteorological

Some

meteorological Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not ...

conditions, especially rapid changes in barometric pressure, as seen with the passing of a front, can displace bodies of water enough to cause trains of waves with wavelengths. These are comparable to seismic tsunamis, but usually with lower energies. Essentially, they are dynamically equivalent to seismic tsunamis, the only differences being 1) that meteotsunamis lack the transoceanic reach of significant seismic tsunamis, and 2) that the force that displaces the water is sustained over some length of time such that meteotsunamis cannot be modelled as having been caused instantaneously. In spite of their lower energies, on shorelines where they can be amplified by resonance, they are sometimes powerful enough to cause localised damage and potential for loss of life. They have been documented in many places, including the Great Lakes, the Aegean Sea, the English Channel, and the Balearic Islands, where they are common enough to have a local name, ''rissaga''. In Sicily they are called ''marubbio'' and in Nagasaki Bay, they are called ''abiki''. Some examples of destructive meteotsunamis include 31 March 1979 at Nagasaki and 15 June 2006 at Menorca, the latter causing damage in the tens of millions of euros. Meteotsunamis should not be confused with

storm surges A storm surge, storm flood, tidal surge, or storm tide is a coastal flood or tsunami-like phenomenon of rising water commonly associated with low-pressure weather systems, such as cyclones. It is measured as the rise in water level above the no ...

, which are local increases in sea level associated with the low barometric pressure of passing tropical cyclones, nor should they be confused with setup, the temporary local raising of sea level caused by strong on-shore winds. Storm surges and setup are also dangerous causes of

coastal flooding Coastal flooding normally occurs when dry and low-lying land is submerged by seawater. The range of a coastal flooding is a result of the elevation of floodwater that penetrates the inland which is controlled by the topography of the coastal land ...

in severe weather but their dynamics are completely unrelated to tsunami waves. They are unable to propagate beyond their sources, as waves do.

Man-made or triggered tsunamis

There have been studies of the potential of the induction of and at least one actual attempt to create tsunami waves as a

tectonic weapon A tectonic weapon is a hypothetical device or system which could trigger earthquakes, volcanic eruptions, or other seismic events in specified locations by interfering with the Earth's natural geological processes. It was defined in 1992 by Aleksey ...

. In World War II, the

New Zealand Military Forces , image = New Zealand Army Logo.png , image_size = 175px , caption = , start_date = , country = , branch = ...

initiated

Project Seal The tsunami bomb was an attempt during World War II to develop a tectonic weapon that could create destructive tsunamis. The project commenced after US Navy officer E.A. Gibson noticed small waves generated by explosions used to clear coral reef ...

, which attempted to create small tsunamis with explosives in the area of today's

Shakespear Regional Park Shakespear Regional Park is a nature park in the Auckland Region of New Zealand. It is located at the tip of the Whangaparaoa Peninsula, and is named after the Shakespear family which bought the land in the 1880s from local Maori. ...

; the attempt failed. There has been considerable speculation on the possibility of using

nuclear weapons A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions (thermonuclear bomb), producing a nuclear explosion. Both bomb ...

to cause tsunamis near an enemy coastline. Even during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

consideration of the idea using conventional explosives was explored. Nuclear testing in the

Pacific Proving Ground The Pacific Proving Grounds was the name given by the United States government to a number of sites in the Marshall Islands and a few other sites in the Pacific Ocean at which it conducted nuclear testing between 1946 and 1962. The U.S. tested ...

by the United States seemed to generate poor results. ''Operation Crossroads'' fired two bombs, one in the air and one underwater, above and below the shallow () waters of the

Bikini Atoll Bikini Atoll ( or ; Marshallese: , , meaning "coconut place"), sometimes known as Eschscholtz Atoll between the 1800s and 1946 is a coral reef in the Marshall Islands consisting of 23 islands surrounding a central lagoon. After the Second ...

lagoon. Fired about from the nearest island, the waves there were no higher than upon reaching the shoreline. Other underwater tests, mainly ''

Hardtack I Operation Hardtack I was a series of 35 nuclear tests conducted by the United States from April 28 to August 18 in 1958 at the Pacific Proving Grounds. At the time of testing, the Operation Hardtack I test series included more nuclear detonation ...

/Wahoo'' (deep water) and ''Hardtack I/Umbrella'' (shallow water) confirmed the results. Analysis of the effects of shallow and deep underwater explosions indicate that the energy of the explosions does not easily generate the kind of deep, all-ocean waveforms which are tsunamis; most of the energy creates steam, causes vertical fountains above the water, and creates compressional waveforms. Tsunamis are hallmarked by permanent large vertical displacements of very large volumes of water which do not occur in explosions.

Characteristics

Propagation du tsunami en profondeur variable

Tsunamis are caused by earthquakes, landslides, volcanic explosions, glacier calvings, and

bolide A bolide is normally taken to mean an exceptionally bright meteor, but the term is subject to more than one definition, according to context. It may refer to any large crater-forming body, or to one that explodes in the atmosphere. It can be a ...

s. They cause damage by two mechanisms: the smashing force of a wall of water travelling at high speed, and the destructive power of a large volume of water draining off the land and carrying a large amount of debris with it, even with waves that do not appear to be large. While everyday

wind wave In fluid dynamics, a wind wave, water wave, or wind-generated water wave, is a surface wave that occurs on the free surface of bodies of water as a result from the wind blowing over the water surface. The contact distance in the direction of t ...

s have a

(from crest to crest) of about and a height of roughly , a tsunami in the deep ocean has a much larger wavelength of up to . Such a wave travels at well over , but owing to the enormous wavelength the wave oscillation at any given point takes 20 or 30 minutes to complete a cycle and has an amplitude of only about . This makes tsunamis difficult to detect over deep water, where ships are unable to feel their passage. The velocity of a tsunami can be calculated by obtaining the square root of the depth of the water in metres multiplied by the acceleration due to gravity (approximated to 10 m/s²). For example, if the Pacific Ocean is considered to have a depth of 5000 metres, the velocity of a tsunami would be = ≈ , which equates to a speed of about . This is the formula used for calculating the velocity of shallow-water waves. Even the deep ocean is shallow in this sense because a tsunami wave is so long (horizontally from crest to crest) by comparison. The reason for the Japanese name "harbour wave" is that sometimes a village's

fishermen A fisher or fisherman is someone who captures fish and other animals from a body of water, or gathers shellfish. Worldwide, there are about 38 million commercial and subsistence fishers and fish farmers. Fishers may be professional or recreat ...

would sail out, and encounter no unusual waves while out at sea fishing, and come back to land to find their village devastated by a huge wave. As the tsunami approaches the coast and the waters become shallow,

compresses the wave and its speed decreases below . Its wavelength diminishes to less than and its amplitude grows enormously—in accord with Green's law. Since the wave still has the same very long

, the tsunami may take minutes to reach full height. Except for the very largest tsunamis, the approaching wave does not

break Break or Breaks or The Break may refer to: Time off from duties * Recess (break), time in which a group of people is temporarily dismissed from its duties * Break (work), time off during a shift/recess ** Coffee break, a short mid-morning rest ...

, but rather appears like a fast-moving

. Open bays and coastlines adjacent to very deep water may shape the tsunami further into a step-like wave with a steep-breaking front. When the tsunami's wave peak reaches the shore, the resulting temporary rise in sea level is termed ''run up''. Run up is measured in metres above a reference sea level. A large tsunami may feature multiple waves arriving over a period of hours, with significant time between the wave crests. The first wave to reach the shore may not have the highest run-up. About 80% of tsunamis occur in the Pacific Ocean, but they are possible wherever there are large bodies of water, including lakes. However, tsunami interactions with shorelines and the seafloor topography are extremely complex, which leaves some countries more vulnerable than others. For example, the Pacific coasts of the United States and Mexico lie adjacent to each other, but the United States has recorded ten tsunamis in the region since 1788, while Mexico has recorded twenty-five since 1732. Similarly, Japan has had more than a hundred tsunamis in recorded history, while the neighboring island of Taiwan has registered only two, in 1781 and 1867.

Drawback

All

wave In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (res ...

s have a positive and negative peak; that is, a ridge and a trough. In the case of a propagating wave like a tsunami, either may be the first to arrive. If the first part to arrive at the shore is the ridge, a massive breaking wave or sudden flooding will be the first effect noticed on land. However, if the first part to arrive is a trough, a drawback will occur as the shoreline recedes dramatically, exposing normally submerged areas. The drawback can exceed hundreds of metres, and people unaware of the danger sometimes remain near the shore to satisfy their curiosity or to collect fish from the exposed seabed. A typical wave period for a damaging tsunami is about twelve minutes. Thus, the sea recedes in the drawback phase, with areas well below sea level exposed after three minutes. For the next six minutes, the wave trough builds into a ridge which may flood the coast, and destruction ensues. During the next six minutes, the wave changes from a ridge to a trough, and the flood waters recede in a second drawback. Victims and debris may be swept into the ocean. The process repeats with succeeding waves.

Scales of intensity and magnitude

As with earthquakes, several attempts have been made to set up scales of tsunami intensity or magnitude to allow comparison between different events.

Intensity scales

The first scales used routinely to measure the intensity of tsunamis were the '' Sieberg- Ambraseys scale'' (1962), used in the

and the ''Imamura-Iida intensity scale'' (1963), used in the Pacific Ocean. The latter scale was modified by Soloviev (1972), who calculated the tsunami intensity "''I''" according to the formula: :

\mathit = \frac + \log_ \mathit_

where

\mathit_

is the "tsunami height" in meters, averaged along the nearest coastline, with the tsunami height defined as the rise of the water level above the normal tidal level at the time of occurrence of the tsunami. This scale, known as the ''Soloviev-Imamura tsunami intensity scale'', is used in the global tsunami catalogues compiled by the NGDC/NOAA and the Novosibirsk Tsunami Laboratory as the main parameter for the size of the tsunami. This formula yields: * ''I'' = 2 for

\mathit_

= 2.8 metres * ''I'' = 3 for

\mathit_

= 5.5 metres * ''I'' = 4 for

\mathit_

= 11 metres * ''I'' = 5 for

\mathit_

= 22.5 metres * etc. In 2013, following the intensively studied tsunamis in 2004 and 2011, a new 12-point scale was proposed, the Integrated Tsunami Intensity Scale (ITIS-2012), intended to match as closely as possible to the modified ESI2007 and EMS earthquake intensity scales.

Magnitude scales

The first scale that genuinely calculated a magnitude for a tsunami, rather than an intensity at a particular location was the ML scale proposed by Murty & Loomis based on the potential energy. Difficulties in calculating the potential energy of the tsunami mean that this scale is rarely used. Abe introduced the ''tsunami magnitude scale

\mathit_

'', calculated from, :

\mathit_ =  \log h +  \log R + \mathit

where ''h'' is the maximum tsunami-wave amplitude (in m) measured by a tide gauge at a distance ''R'' from the epicentre, ''a'', ''b'' and ''D'' are constants used to make the M_t scale match as closely as possible with the moment magnitude scale.

Tsunami heights

Several terms are used to describe the different characteristics of tsunami in terms of their height: *Amplitude, Wave Height, or Tsunami Height: Refers to the height of a tsunami relative to the normal sea level at the time of the tsunami, which may be tidal High Water, or Low Water. It is different from the crest-to-trough height which is commonly used to measure other type of wave height. *Run-up Height, or Inundation Height: The height reached by a tsunami on the ground above sea level, Maximum run-up height refers to the maximum height reached by water above sea level, which is sometimes reported as the maximum height reached by a tsunami. *Flow Depth: Refers to the height of tsunami above ground, regardless of the height of the location or sea level. *(Maximum) Water Level: Maximum height above sea level as seen from trace or water mark. Different from maximum run-up height in the sense that they are not necessarily water marks at inundation line/limit.

Warnings and predictions

Calculated Travel Time Map for 1964 Alaska Tsunami

Drawbacks can serve as a brief warning. People who observe drawback (many survivors report an accompanying sucking sound), can survive only if they immediately run for high ground or seek the upper floors of nearby buildings. In 2004, ten-year-old

Tilly Smith Tilly Smith (born 1994) is an English woman who has been credited with saving the lives of about 100 beachgoers at Mai Khao Beach in Thailand by warning them minutes before the arrival of the tsunami caused by the 2004 Indian Ocean earthquake. Sm ...

Surrey Surrey () is a ceremonial and non-metropolitan county in South East England, bordering Greater London to the south west. Surrey has a large rural area, and several significant urban areas which form part of the Greater London Built-up Area. ...

, England, was on Maikhao beach in

Phuket Phuket (; th, ภูเก็ต, , ms, Bukit or ''Tongkah''; Hokkien:普吉; ) is one of the southern provinces (''changwat'') of Thailand. It consists of the island of Phuket, the country's largest island, and another 32 smaller islands of ...

, Thailand with her parents and sister, and having learned about tsunamis recently in school, told her family that a tsunami might be imminent. Her parents warned others minutes before the wave arrived, saving dozens of lives. She credited her geography teacher, Andrew Kearney. In the

drawback was not reported on the African coast or any other east-facing coasts that it reached. This was because the initial wave moved downwards on the eastern side of the megathrust and upwards on the western side. The western pulse hit coastal Africa and other western areas. A tsunami cannot be precisely predicted, even if the magnitude and location of an earthquake is known.

Geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, althou ...

oceanographer Oceanography (), also known as oceanology and ocean science, is the scientific study of the oceans. It is an Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamics ...

s, and

seismologist Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...

s analyse each earthquake and based on many factors may or may not issue a tsunami warning. However, there are some warning signs of an impending tsunami, and automated systems can provide warnings immediately after an earthquake in time to save lives. One of the most successful systems uses bottom pressure sensors, attached to buoys, which constantly monitor the pressure of the overlying water column. Regions with a high tsunami risk typically use

tsunami warning system A tsunami warning system (TWS) is used to detect tsunamis in advance and issue the warnings to prevent loss of life and damage to property. It is made up of two equally important components: a network of sensors to detect tsunamis and a communica ...

s to warn the population before the wave reaches land. On the west coast of the United States, which is prone to tsunamis from the Pacific Ocean, warning signs indicate evacuation routes. In Japan, the populace is well-educated about earthquakes and tsunamis, and along Japanese shorelines, tsunami warning signs remind people of the natural hazards along with a network of warning sirens, typically at the top of the cliffs of surrounding hills. The Pacific Tsunami Warning System is based in

Honolulu Honolulu (; ) is the capital and largest city of the U.S. state of Hawaii, which is in the Pacific Ocean. It is an unincorporated county seat of the consolidated City and County of Honolulu, situated along the southeast coast of the island ...

. It monitors Pacific Ocean seismic activity. A sufficiently large earthquake magnitude and other information triggers a tsunami warning. While the subduction zones around the Pacific are seismically active, not all earthquakes generate a tsunami. Computers assist in analysing the tsunami risk of every earthquake that occurs in the Pacific Ocean and the adjoining land masses. File:Bamfield Tsunami Hazard Zone sign.jpg, Tsunami hazard sign at

Bamfield Bamfield is a community that is surrounded by Crown Land, First Nation Lands belonging to the Huu-ay-aht Nations, and portions of the Pacific Rim National Park, located on Barkley Sound, Vancouver Island in British Columbia. The community, with ...

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

File: A tsunami warning sign in Kamakura, Japan.jpg, A tsunami warning sign in

Kamakura is a city in Kanagawa Prefecture, Japan. Kamakura has an estimated population of 172,929 (1 September 2020) and a population density of 4,359 persons per km² over the total area of . Kamakura was designated as a city on 3 November 1939. Kamak ...

, Japan File:Zona de Inundabilidad.jpg, A Tsunami hazard sign (Spanish - English) in

Iquique Iquique () is a port city and commune in northern Chile, capital of both the Iquique Province and Tarapacá Region. It lies on the Pacific coast, west of the Pampa del Tamarugal, which is part of the Atacama Desert. It has a population of 191,468 ...

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

. File:Tsunami Evacuation Route signage south of Aberdeen Washington.jpg, alt=Photo of evacuation sign, Tsunami Evacuation Route signage along

U.S. Route 101 U.S. Route 101, or U.S. Highway 101 (US 101), is a north–south United States Numbered Highway that runs through the states of California, Oregon, and Washington, on the West Coast of the United States. It is also known as (The Royal Roa ...

, in

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered on ...

As a direct result of the Indian Ocean tsunami, a re-appraisal of the tsunami threat for all coastal areas is being undertaken by national governments and the United Nations Disaster Mitigation Committee. A tsunami warning system is being installed in the Indian Ocean. Dart tsunamicover

Computer model Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be deter ...

s can predict tsunami arrival, usually within minutes of the arrival time. Bottom pressure sensors can relay information in

real time Real-time or real time describes various operations in computing or other processes that must guarantee response times within a specified time (deadline), usually a relatively short time. A real-time process is generally one that happens in defined ...

. Based on these pressure readings and other seismic information and the seafloor's shape (

bathymetry Bathymetry (; ) is the study of underwater depth of ocean floors (''seabed topography''), lake floors, or river floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water de ...

) and coastal

topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...

, the models estimate the amplitude and surge height of the approaching tsunami. All

Pacific Rim The Pacific Rim comprises the lands around the rim of the Pacific Ocean. The ''Pacific Basin'' includes the Pacific Rim and the islands in the Pacific Ocean. The Pacific Rim roughly overlaps with the geologic Pacific Ring of Fire. List of co ...

countries collaborate in the Tsunami Warning System and most regularly practise evacuation and other procedures. In Japan, such preparation is mandatory for government, local authorities, emergency services and the population. Along the United States west coast, in addition to sirens, warnings are sent on television and radio via the

National Weather Service The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...

, using the

Emergency Alert System The Emergency Alert System (EAS) is a national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via cable, satellite, or broadcast television, and both ...

Possible animal reaction

Some zoologists hypothesise that some animal species have an ability to sense subsonic

Rayleigh waves Rayleigh waves are a type of surface acoustic wave that travel along the surface of solids. They can be produced in materials in many ways, such as by a localized impact or by piezo-electric transduction, and are frequently used in non-destructive ...

from an earthquake or a tsunami. If correct, monitoring their behaviour could provide advance warning of earthquakes and tsunamis. However, the evidence is controversial and is not widely accepted. There are unsubstantiated claims about the Lisbon quake that some animals escaped to higher ground, while many other animals in the same areas drowned. The phenomenon was also noted by media sources in

Sri Lanka Sri Lanka (, ; si, ශ්‍රී ලංකා, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon and officially the Democratic Socialist Republic of Sri Lanka, is an ...

in the

. It is possible that certain animals (e.g.,

elephant Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantidae an ...

s) may have heard the sounds of the tsunami as it approached the coast. The elephants' reaction was to move away from the approaching noise. By contrast, some humans went to the shore to investigate and many drowned as a result.

Mitigation

In some tsunami-prone countries,

earthquake engineering Earthquake engineering is an interdisciplinary branch of engineering that designs and analyzes structures, such as buildings and bridges, with earthquakes in mind. Its overall goal is to make such structures more resistant to earthquakes. An earth ...

measures have been taken to reduce the damage caused onshore.

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

, where tsunami science and response measures first began following a disaster in 1896, has produced ever-more elaborate countermeasures and response plans. The country has built many tsunami walls of up to high to protect populated coastal areas. Other localities have built

floodgate Floodgates, also called stop gates, are adjustable gates used to control water flow in flood barriers, reservoir, river, stream, or levee systems. They may be designed to set spillway crest heights in dams, to adjust flow rates in sluices and c ...

s of up to high and channels to redirect the water from an incoming tsunami. However, their effectiveness has been questioned, as tsunamis often overtop the barriers. The

Fukushima Daiichi nuclear disaster The was a nuclear accident in 2011 at the Fukushima Daiichi Nuclear Power Plant in Ōkuma, Fukushima, Japan. The proximate cause of the disaster was the 2011 Tōhoku earthquake and tsunami, which occurred on the afternoon of 11 March 2011 and ...

was directly triggered by the

2011 Tōhoku earthquake and tsunami The occurred at 14:46 JST (05:46 UTC) on 11 March. The magnitude 9.0–9.1 (M) undersea megathrust earthquake had an epicenter in the Pacific Ocean, east of the Oshika Peninsula of the Tōhoku region, and lasted approximately six minutes ...

, when waves exceeded the height of the plant's sea wall.Phillip Lipscy, Kenji Kushida, and Trevor Incerti. 2013.
The Fukushima Disaster and Japan’s Nuclear Plant Vulnerability in Comparative Perspective
". ''Environmental Science and Technology'' 47 (May), 6082–6088.

Iwate Prefecture is a prefecture of Japan located in the Tōhoku region of Honshu. It is the second-largest Japanese prefecture at , with a population of 1,210,534 (as of October 1, 2020). Iwate Prefecture borders Aomori Prefecture to the north, Akita Prefectur ...

, which is an area at high risk from tsunami, had tsunami barriers walls ( Taro sea wall) totalling long at coastal towns. The 2011 tsunami toppled more than 50% of the walls and caused catastrophic damage. The Okushiri, Hokkaidō tsunami which struck

Okushiri Island is an island in Hokkaidō, Japan. It has an area of . The town of Okushiri and the Hiyama Prefectural Natural Park encompass the entire island. It has many pastures, beech tree forests, and a rocky coastline. There are two elementary schools, on ...

Hokkaidō is Japan's second largest island and comprises the largest and northernmost prefecture, making up its own region. The Tsugaru Strait separates Hokkaidō from Honshu; the two islands are connected by the undersea railway Seikan Tunnel. The la ...

within two to five minutes of the earthquake on July 12, 1993, created waves as much as tall—as high as a 10-storey building. The port town of Aonae was completely surrounded by a tsunami wall, but the waves washed right over the wall and destroyed all the wood-framed structures in the area. The wall may have succeeded in slowing down and moderating the height of the tsunami, but it did not prevent major destruction and loss of life.

Footnotes

References

IOC Tsunami Glossary
by the

Intergovernmental Oceanographic Commission The Intergovernmental Oceanographic Commission of UNESCO (IOC/UNESCO) was established by resolution 2.31 adopted by the General Conference of UNESCO. It first met in Paris at Unesco Headquarters from 19 to 27 October 1961. Initially, 40 States becam ...

(IOC) at th
International Tsunami Information Centre
(ITIC) of

UNESCO The United Nations Educational, Scientific and Cultural Organization is a specialized agency of the United Nations (UN) aimed at promoting world peace and security through international cooperation in education, arts, sciences and culture. It ...

Tsunami Terminology
at

NOAA The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...

*In June 2011, the VOA

Special English Learning English (previously known as Special English) is a controlled version of the English language first used on 19 October 1959, and still presented daily by the United States broadcasting service Voice of America (VOA). World news and othe ...

service of the

Voice of America Voice of America (VOA or VoA) is the state-owned news network and international radio broadcaster of the United States of America. It is the largest and oldest U.S.-funded international broadcaster. VOA produces digital, TV, and radio content ...

broadcast a 15-minute program on tsunamis as part of its weekly Science in the News series. The program included an interview with an NOAA official who oversees the agency's tsunami warning system. A transcript and MP3 of the program, intended for English learners, can be found a
The Ever-Present Threat of Tsunamis.

abelard.org.
''tsunamis: tsunamis travel fast but not at infinite speed''. retrieved March 29, 2005. * Dudley, Walter C. & Lee, Min (1988: 1st edition) ''Tsunami!''

* Iwan, W.D., ''editor'', 2006, Summary report of the Great Sumatra Earthquakes and Indian Ocean tsunamis of December 26, 2004 and March 28, 2005: Earthquake Engineering Research Institute, EERI Publication #2006-06, 11 chapters, 100-page summary, plus CD-ROM with complete text and supplementary photographs, EERI Report 2006–06.
website
* Kenneally, Christine (December 30, 2004). "Surviving the Tsunami." ''Slate''
website
* Lambourne, Helen (March 27, 2005). "Tsunami: Anatomy of a disaster." ''

BBC News BBC News is an operational business division of the British Broadcasting Corporation (BBC) responsible for the gathering and broadcasting of news and current affairs in the UK and around the world. The department is the world's largest broadca ...

''
website
* Macey, Richard (January 1, 2005). "The Big Bang that Triggered A Tragedy," ''

The Sydney Morning Herald ''The Sydney Morning Herald'' (''SMH'') is a daily compact newspaper published in Sydney, New South Wales, Australia, and owned by Nine. Founded in 1831 as the ''Sydney Herald'', the ''Herald'' is the oldest continuously published newspaper ...

'', p 11—quoting Dr Mark Leonard, seismologist at Geoscience Australia.
Interactive Map of Historical Tsunamis
from NOAA National Centers for Environmental Information * Tappin, D; 2001. Local tsunamis. Geoscientist. 11–8, 4–7.

''

Telegraph.co.uk ''The Daily Telegraph'', known online and elsewhere as ''The Telegraph'', is a national British daily broadsheet newspaper published in London by Telegraph Media Group and distributed across the United Kingdom and internationally. It was fo ...

''
Philippines warned to prepare for Japan's tsunami
''Noypi.ph''

External links

World's Tallest Tsunami
– geology.com
Tsunami Data and Information
–

National Centers for Environmental Information The National Centers for Environmental Information (NCEI), an agency of the United States government, manages one of the world's largest archives of atmospheric, coastal, geophysical, and oceanic data, containing information that ranges from th ...

IOC Tsunami Glossary
– International Tsunami Information Center (

)
Tsunami & Earthquake Research at the USGS
–

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

Intergovernmental Oceanographic Commission
–

Tsunami
–

National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...

Wave That Shook The World
– ''

Nova A nova (plural novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", which is Latin for "new") that slowly fades over weeks or months. Causes of the dramati ...

''
Recent and Historical Tsunami Events and Relevant Data
–

Pacific Marine Environmental Laboratory The Pacific Marine Environmental Laboratory (PMEL) is a federal laboratory in the National Oceanic and Atmospheric Administration (NOAA) Office of Oceanic and Atmospheric Research (OAR). It is one of seven NOAA Research Laboratories (RLs). The PM ...

Raw Video: Tsunami Slams Northeast Japan
–

Associated Press The Associated Press (AP) is an American non-profit news agency headquartered in New York City. Founded in 1846, it operates as a cooperative, unincorporated association. It produces news reports that are distributed to its members, U.S. newspa ...

Tsunami alert
page (in English) from

Japan Meteorological Agency The , abbreviated JMA, is an agency of the Ministry of Land, Infrastructure, Transport and Tourism. It is charged with gathering and providing results for the public in Japan that are obtained from data based on daily scientific observation an ...

Tsunami status page
from

USGS The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, a ...

-run

Pacific Tsunami Warning Center The Pacific Tsunami Warning Center (PTWC) is one of two tsunami warning centers that are operated by NOAA in the United States. Headquartered on Ford Island, HI, the PTWC is part of an international tsunami warning system (TWS) program and s ...

Tsunami animation – Geoscience Australia
{{Authority control Articles containing video clips

Terminology

Tsunami

Tidal wave

Seismic sea wave

History

Causes

Seismicity

Landslides

Volcanic eruptions

Meteorological

Man-made or triggered tsunamis

Characteristics

Drawback

Scales of intensity and magnitude

Intensity scales

Magnitude scales

Tsunami heights

Warnings and predictions

Possible animal reaction

Mitigation

See also

Footnotes

References

Further reading

External links