Tsunami waves do not resemble normal undersea currents or sea waves because their wavelength is far longer.[7] Rather than appearing as a breaking wave, a tsunami may instead initially resemble a rapidly rising tide.[8] For this reason, it is often referred to as a tidal wave,[9] 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.[10] Tsunamis generally consist of a series of waves, with periods ranging from minutes to hours, arriving in a so-called "wave train."[11] 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 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 Ancient Greek historian Thucydides suggested in his 5th century BC History of the Peloponnesian War that tsunamis were related to submarine earthquakes,[12][13] 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.
The term "tsunami" is a borrowing from the Japanese tsunami津波,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.[14] Some English speakers alter the word's initial /ts/ to an /s/ by dropping the "t," since English does not natively permit /ts/ at the beginning of words,though the original Japanese pronunciation is /ts/.
Tsunamis are sometimes referred to as tidal waves.[15] This once-popular term derives from the most common appearance of a tsunami,which is that of an extraordinarily high tidal bore. 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 tides,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"[16] or "having the form or character of"[17] tides,use of the term tidal wave is discouraged by geologists and oceanographers.
A 1969 episode of the TV crime show Hawaii Five-O entitled "Forty Feet High and It Kills!" used the terms "tsunami" and "tidal wave" interchangeably.[18]
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 activity such as earthquakes.[19] 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 landslides,volcanic eruptions,underwater explosions,land or ice slumping into the ocean,meteorite impacts,and the weather when the atmospheric pressure changes very rapidly—can generate such waves by displacing water.[20][21]
While Japan may have the longest recorded history of tsunamis,the sheer destruction caused by the 2004 Indian Ocean earthquake and tsunami event mark it as the most devastating of its kind in modern times,killing around 230,000 people.[22] The Sumatran region is also accustomed to tsunamis,with earthquakes of varying magnitudes regularly occurring off the coast of the island.[23]
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.[24]
The Roman historian Ammianus Marcellinus (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.[25][26]
Causes
The principal generation mechanism of a tsunami is the displacement of a substantial volume of water or perturbation of the sea.[27] This displacement of water is usually attributed to either earthquakes,landslides,volcanic eruptions,glacier calvings or more rarely by meteorites and nuclear tests.[28][29] However,the possibility of a meteorite causing a tsunami is debated.[30]
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.[31] More specifically,a tsunami can be generated when thrust faults associated with convergent or destructive plate boundaries 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) cause enough displacement to give rise to a significant tsunami,such as the 1977 Sumba and 1933 Sanriku events.[32][33]
Over-riding plate bulges under strain,causing tectonic uplift.
Plate slips,causing subsidence and releasing energy into water.
The energy released produces tsunami waves.
Tsunamis have a small wave height offshore,and a very long wavelength (often hundreds of kilometres long,whereas normal ocean waves have a wavelength of only 30 or 40 metres),[34] which is why they generally pass unnoticed at sea,forming only a slight swell usually about 300 millimetres (12in) above the normal sea surface. They grow in height when they reach shallower water,in a wave shoaling 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 MwAleutian Islands earthquake occurred with a maximum Mercalli intensity of VI (Strong). It generated a tsunami which inundated Hilo on the island of Hawaii with a 14-metre high (46ft) surge. Between 165 and 173 were killed. The area where the earthquake occurred is where the Pacific Ocean floor is subducting (or being pushed downwards) under Alaska.
Examples of tsunamis originating at locations away from convergent boundaries include Storegga about 8,000 years ago,Grand Banks in 1929,and Papua New Guinea 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.).
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,Alaska,caused the highest wave ever recorded,which had a height of 524 metres (1,719ft).[35] 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.[36][37][38]
Another landslide-tsunami event occurred in 1963 when a massive landslide from Monte Toc entered the reservoir behind the Vajont Dam in Italy. The resulting wave surged over the 262-metre (860ft)-high dam by 250 metres (820ft) and destroyed several towns. Around 2,000 people died.[39][40] Scientists named these waves megatsunamis.
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,Fogo in the Cape Verde Islands,La Reunion in the Indian Ocean,and Cumbre Vieja on the island of La Palma in the Canary Islands;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.[41]
Some meteorological 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.[42]
Meteotsunamis should not be confused with storm surges,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 in severe weather but their dynamics are completely unrelated to tsunami waves.[42] They are unable to propagate beyond their sources,as waves do.
There has been considerable speculation on the possibility of using nuclear weapons to cause tsunamis near an enemy coastline. Even during World War II consideration of the idea using conventional explosives was explored. Nuclear testing in the Pacific Proving Ground by the United States seemed to generate poor results. Operation Crossroads fired two 20 kilotonnes of TNT (84TJ) bombs,one in the air and one underwater,above and below the shallow (50m (160ft)) waters of the Bikini Atoll lagoon. Fired about 6km (3.7mi) from the nearest island,the waves there were no higher than 3–4m (9.8–13.1ft) upon reaching the shoreline. Other underwater tests,mainly Hardtack I/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.[44] Tsunamis are hallmarked by permanent large vertical displacements of very large volumes of water which do not occur in explosions.
Characteristics
When the wave enters shallow water,it slows down and its amplitude (height) increases.The wave further slows and amplifies as it hits land. Only the largest waves crest.
Tsunamis 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 waves have a wavelength (from crest to crest) of about 100 metres (330ft) and a height of roughly 2 metres (6.6ft),a tsunami in the deep ocean has a much larger wavelength of up to 200 kilometres (120mi). Such a wave travels at well over 800 kilometres per hour (500mph),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 1 metre (3.3ft).[45] 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 10m/s2). For example,if the Pacific Ocean is considered to have a depth of 5000 metres,the velocity of a tsunami would be √5000 ×10 = √50000 ≈224 metres per second (730ft/s),which equates to a speed of about 806 kilometres per hour (501mph). 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 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,wave shoaling compresses the wave and its speed decreases below 80 kilometres per hour (50mph). Its wavelength diminishes to less than 20 kilometres (12mi) and its amplitude grows enormously—in accord with Green's law. Since the wave still has the same very long period,the tsunami may take minutes to reach full height. Except for the very largest tsunamis,the approaching wave does not break,but rather appears like a fast-moving tidal bore.[46] 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.[46] 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.[47]
About 80% of tsunamis occur in the Pacific Ocean,but they are possible wherever there are large bodies of water,including lakes. They are caused by earthquakes,landslides,volcanic explosions,glacier calvings,and bolides.
Drawback
An illustration of the rhythmic "drawback" of surface water associated with a wave. It follows that a very large drawback may herald the arrival of a very large wave.
All waves 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.[48]
Intensity scales
The first scales used routinely to measure the intensity of tsunamis were the Sieberg-Ambraseys scale (1962),used in the Mediterranean Sea 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:
where is the "tsunami height," 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.[49] This scale,known as the Soloviev-Imamura tsunami intensity scale,is used in the global tsunami catalogues compiled by the NGDC/NOAA[50] and the Novosibirsk Tsunami Laboratory as the main parameter for the size of the tsunami.
This formula yields:
I = 2 for = 2.8 meters
I = 3 for = 5.5 meters
I = 4 for = 11 meters
I = 5 for = 22.5 meters
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.[51][52]
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.[48] Difficulties in calculating the potential energy of the tsunami mean that this scale is rarely used. Abe introduced the tsunami magnitude scale ,calculated from,
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 Mt scale match as closely as possible with the moment magnitude scale.[53]
Tsunami heights
Diagram showing several measures to describe a tsunami size,including height,inundation and run-up.
Several terms are used to describe the different characteristics of tsunami in terms of their height:[54][55][56][57]
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.[58]
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.
Calculated travel time map for the 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 of Surrey,England,was on Maikhao beach in Phuket,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 2004 Indian Ocean tsunami 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. Geologists,oceanographers,and seismologists 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 systems to warn the population before the wave reaches land. On the west coast of the United States,which is prone to Pacific Ocean tsunami,warning signs indicate evacuation routes. In Japan,the community is well-educated about earthquakes and tsunamis,and along the Japanese shorelines the tsunami warning signs are reminders of the natural hazards together with a network of warning sirens,typically at the top of the cliff of surroundings hills.[59]
The Pacific Tsunami Warning System is based in Honolulu,Hawaiʻi. 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.
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.
One of the deep water buoys used in the DART tsunami warning system
Computer models can predict tsunami arrival,usually within minutes of the arrival time. Bottom pressure sensors can relay information in real time. Based on these pressure readings and other seismic information and the seafloor's shape (bathymetry) and coastal topography,the models estimate the amplitude and surge height of the approaching tsunami. All Pacific Rim 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.
Some zoologists hypothesise that some animal species have an ability to sense subsonic Rayleigh waves 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 in the 2004 Indian Ocean earthquake.[60][61] It is possible that certain animals (e.g.,elephants) 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.
In some tsunami-prone countries,earthquake engineering measures have been taken to reduce the damage caused onshore.
Japan,where tsunami science and response measures first began following a disaster in 1896,has produced ever-more elaborate countermeasures and response plans.[62] The country has built many tsunami walls of up to 12 metres (39ft) high to protect populated coastal areas. Other localities have built floodgates of up to 15.5 metres (51ft) high and channels to redirect the water from an incoming tsunami. However,their effectiveness has been questioned,as tsunamis often overtop the barriers.
The Okushiri,Hokkaidōtsunami which struck Okushiri Island of Hokkaidō within two to five minutes of the earthquake on July 12,1993,created waves as much as 30 metres (100ft) 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.[65]
↑ Glasstone, Samuel; Dolan, Philip (1977). Shock effects of surface and subsurface bursts – The effects of nuclear weapons (thirded.). Washington, DC: U.S. Department of Defense; Energy Research and Development Administration.
↑ Lekkas E.; Andreadakis E.; Kostaki I. & Kapourani E. (2013). "A Proposal for a New Integrated Tsunami Intensity Scale (ITIS‐2012)". Bulletin of the Seismological Society of America. 103 (2B): 1493–1502. Bibcode:2013BuSSA.103.1493L. doi:10.1785/0120120099.
An earthquake 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 size from those that are so weak that they cannot be felt to those violent enough to propel objects and people into the air, and wreak destruction across entire cities. The seismicity, or seismic activity, of an area is the frequency, type, and size of earthquakes experienced over a period of time. The word tremor is also used for non-earthquake seismic rumbling.
A megatsunami is a very large wave created by a large, sudden displacement of material into a body of water.
Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters.
A seiche is a standing wave in an enclosed or partially enclosed body of water. Seiches and seiche-related phenomena have been observed on lakes, reservoirs, swimming pools, bays, harbours and seas. The key requirement for formation of a seiche is that the body of water be at least partially bounded, allowing the formation of the standing wave.
The Cumbre Vieja 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, and covers the southern half of La Palma, with both summit ridge and flanks pockmarked by over a dozen craters. The latest eruption, currently ongoing, began on 19 September 2021 in a forested area of Las Manchas locality known as Cabeza de Vaca. Lava flows from the new vent soon reached inhabited areas; thousands of residents were evacuated, and thousands of buildings have since been destroyed. The previous two eruptions on the island were in the 20th century, in 1949 and in 1971.
The 2004 Indian Ocean earthquake and tsunami occurred at 07:58:53 in local time (UTC+7) on 26 December, with an epicentre off the west coast of northern Sumatra, Indonesia. It was an undersea megathrust earthquake that registered a magnitude of 9.1–9.3 Mw, reaching a Mercalli intensity up to IX in certain areas. The earthquake was caused by a rupture along the fault between the Burma Plate and the Indian Plate.
The 1929 Grand Banks earthquake occurred on November 18, 1929. The shock had a moment magnitude of 7.2 and a maximum Rossi–Forel intensity of VI and was centered in the Atlantic Ocean off the south coast of Newfoundland in the Laurentian Slope Seismic Zone.
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 communications infrastructure to issue timely alarms to permit evacuation of the coastal areas. There are two distinct types of tsunami warning systems: international and regional. When operating, seismic alerts are used to instigate the watches and warnings; then, data from observed sea level height are used to verify the existence of a tsunami. Other systems have been proposed to augment the warning procedures; for example, it has been suggested that the duration and frequency content of t-wave energy is indicative of an earthquake's tsunami potential.
The seismicity of the Sanriku coast identifies and describes the seismic activity of an area of Japan. Seismicity refers to the frequency, type and size of earthquakes experienced over a period of time. The Sanriku coast is a descriptive term referring to the coastal areas of the former provinces of Rikuō in Aomori, Rikuchū in Aomori, and Rikuzen in Miyagi.
A meteotsunami or meteorological tsunami is a tsunami-like sea wave of meteorological origin. Meteotsunamis are generated when rapid changes in barometric pressure cause the displacement of a body of water. In contrast to "ordinary" impulse-type tsunami sources, a traveling atmospheric disturbance normally interacts with the ocean over a limited period of time. Tsunamis and meteotsunamis are otherwise similar enough that it can be difficult to distinguish one from the other, as in cases where there is a tsunami wave but there are no seismic records of an earthquake. Meteotsunamis, rather, are triggered due to extreme weather events including severe thunderstorms, squalls and storm fronts; all of which can quickly change atmospheric pressure. Meteotsunamis typically occur when severe weather is moving at the same speed and direction of the local wave action towards the coastline. The size of the wave is enhanced by coastal features such as shallow continental shelves, bays and inlets.
The 2006 Pangandaran earthquake and tsunami occurred on July 17 at 15:19:27 local time along a subduction zone off the coast of west and central Java, a large and densely populated island in the Indonesian archipelago. The shock had a moment magnitude of 7.7 and a maximum perceived intensity of IV (Light) in Jakarta, the capital and largest city of Indonesia. There were no direct effects of the earthquake's shaking due to its low intensity, and the large loss of life from the event was due to the resulting tsunami, which inundated a 300 km (190 mi) portion of the Java coast that had been unaffected by the earlier 2004 Indian Ocean earthquake and tsunami that was off the coast of Sumatra. The July 2006 earthquake was also centered in the Indian Ocean, 180 kilometers (110 mi) from the coast of Java, and had a duration of more than three minutes.
A natural hazard is a natural phenomenon that might have a negative effect on humans and other animals, or the environment. Natural hazard events can be classified into two broad categories: geophysical and biological.
Submarine landslides are marine landslides that transport sediment across the continental shelf and into the deep ocean. A submarine landslide is initiated when the downwards driving stress exceeds the resisting stress of the seafloor slope material causing movements along one or more concave to planar rupture surfaces. Submarine landslides take place in a variety of different settings including planes as low as 1° and can cause significant damage to both life and property. Recent advances have been made in understanding the nature and processes of submarine landslides through the use of sidescan sonar and other seafloor mapping technology.
A teletsunami is a tsunami that originates from a distant source, defined as more than 1,000 km (620 mi) away or three hours' travel from the area of interest, sometimes travelling across an ocean. All teletsunamis have been generated by major earthquakes such as the 1755 Lisbon earthquake, 1960 Valdivia earthquake, 1964 Alaska earthquake, and 2004 Indian Ocean earthquake.
A tsunami is defined as a series of water waves caused by the displacement of a large volume of a body of water; in the case of this article the body of water being investigated will be a lake rather than an ocean. Tsunamis in lakes are becoming increasingly important to investigate as a hazard, due to the increasing popularity for recreational uses, and increasing populations that inhabit the shores of lakes. Tsunamis generated in lakes and reservoirs are of high concern because it is associated with a near field source region which means a decrease in warning times to minutes or hours.
The 1993 southwest-off Hokkaido earthquake or Okushiri earthquake occurred at 13:17:12 UTC on 12 July 1993 in the Sea of Japan near the island of Hokkaido. It had a magnitude of 7.7 on the moment magnitude scale and a maximum felt intensity of VIII (Severe) on the Mercalli intensity scale. It triggered a major tsunami that caused deaths on Hokkaidō and in southeastern Russia, with a total of 230 fatalities recorded. The island of Okushiri was hardest hit, with 165 casualties from the earthquake, the tsunami and a large landslide.
The Tsunami Warning, Education, and Research Act of 2014 is a bill that would authorize the National Oceanic and Atmospheric Administration (NOAA) to spend $27 million a year for three years on their on-going tsunami warning and research programs.
On April 13, 1923 at 15:31 UTC, an earthquake occurred off the northern coast of the Kamchatka Peninsula in the USSR, present-day Russia. The earthquake had a surface wave magnitude (Ms ) of 6.8 to 7.3 and an estimated moment magnitude (Mw ) of ~8.0. This event came just two months after a slightly larger Mw 8.4 earthquake, with the epicenter south of the April event, struck the area. Both earthquakes were tsunamigenic although the latter generated wave heights far exceeding that of the one in February. After two foreshocks of "moderate force", the main event caused considerable damage. Most of the 36 casualties were the result of the tsunami inundation rather than the earthquake.
The Kaikōura Canyon is a geologically active submarine canyon located southwest of the Kaikōura Peninsula off the northeastern coast of the South Island of New Zealand. It is 60 kilometres (37 mi) long, and is generally U-shaped. The canyon descends into deep water and merges into an ocean channel system that can be traced for hundreds of kilometres across the deep ocean floor. At the head of the Kaikōura Canyon, the depth of water is around 30 metres (98 ft), but it drops rapidly to 600 metres (2,000 ft) and continues down to around 2,000 metres (6,600 ft) deep where it meets the Hikurangi Channel. Sperm whales can be seen close to the coast south of Goose Bay, because the deep water of the Kaikōura Canyon is only one kilometre (0.62 mi) off the shoreline in this area.
In June 2011, the VOA Special English service of the Voice of America 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 at The Ever-Present Threat of Tsunamis.
abelard.org.tsunamis: tsunamis travel fast but not at infinite speed. retrieved March 29, 2005.
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. ISBN1-932884-19-Xwebsite
Kenneally, Christine (December 30, 2004). "Surviving the Tsunami." Slate. website
Lambourne, Helen (March 27, 2005). "Tsunami: Anatomy of a disaster." BBC News. website
Macey, Richard (January 1, 2005). "The Big Bang that Triggered A Tragedy," The Sydney Morning Herald, p 11—quoting Dr Mark Leonard, seismologist at Geoscience Australia.
Boris Levin, Mikhail Nosov: Physics of tsunamis. Springer, Dordrecht 2009, ISBN978-1-4020-8855-1.
Kontar, Y. A. et al.: Tsunami Events and Lessons Learned: Environmental and Societal Significance. Springer, 2014. ISBN978-94-007-7268-7 (print); ISBN978-94-007-7269-4 (eBook)
Kristy F. Tiampo: Earthquakes: simulations, sources and tsunamis. Birkhäuser, Basel 2008, ISBN978-3-7643-8756-3.
Linda Maria Koldau: Tsunamis. Entstehung, Geschichte, Prävention, (Tsunami development, history and prevention) C.H. Beck, Munich 2013 (C.H. Beck Reihe Wissen 2770), ISBN978-3-406-64656-0 (in German).
Walter C. Dudley, Min Lee: Tsunami! University of Hawaii Press, 1988, 1998, Tsunami! University of Hawai'i Press 1999, ISBN0-8248-1125-9, ISBN978-0-8248-1969-9.
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