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    "en": "Tsunami (Submarine Landslide Trigger)"
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    "en": "Tsunami is a Japanese term meaning wave (‘nami’) in a harbour (‘tsu’). It is a series of travelling waves of extremely long length and period. They are usually generated by seabed disturbances associated with earthquakes occurring below or near the ocean floor, but also by other mechanisms such as submarine landslides (IOC, 2019). <br /> <p>IOC, 2019. <a href=\"https://unesdoc.unesco.org/ark:/48223/pf0000188226?posInSet=1&amp;queryId=aeb846ae-edfb-4d66-a03a-385a5d5897f0\">Tsunami Glossary, 2019. Intergovernmental Oceanographic Commission (IOC), Technical Series, 85. Fourth Edition. IOC/2008/TS/85 rev.4</a>.</p>"
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      "Tsunamis are also called seismic sea waves and, incorrectly, tidal waves. Submarine landslides, volcanic eruptions and coastal rock falls also generate tsunamis, as can large meteorites impacting the ocean. Tsunamis are gravity waves that may attain wavelengths of hundreds of miles with periods of 10 to 60 minutes; which allow them to travel across the largest ocean basins with little loss of energy. Tsunami waves steepen and increase in height up to tens and hundreds of meters on entering shallow water, inundating low-lying areas. Where local submarine topography causes the waves to oversteepen, they may break and cause great damage. Tsunamis have no connection with tides; the popular name, tidal wave, is entirely misleading (IOC, 2019). Approximately 80% of tsunami are caused by earthquakes, but more recently it has been recognised that submarine landslides are also a significant tsunami mechanism. The size of the landslides varies from a few (one to six), to thousands of cubic kilometres. The size of the initial wave caused by the submarine landslide varies from a few to hundreds of meters. This initial wave rapidly collapses, and then travels away from the source at speeds of hundreds of kilometres per hour, depending on the water depth, with the deeper the water, the faster the velocity. There are usually a number of tsunami waves, of extremely long (hundreds of kilometres) wavelength, but small (less than one metre) elevation. When the waves approach land, and water depths shallow, they can build to tens or, more rarely, hundreds of metres in height, which can inundate low-lying areas and cause great damage. The tsunami waves caused by submarine landslides, compared to those from earthquakes, are of higher frequency so are very dispersive; unless the landslide is large volume, they do not travel as far. Near to the source mechanism, on striking land they can be elevated (tens to hundreds of metres high), and can be very destructive (Tappin, 2017, 2021). The Intergovernmental Oceanographic Commission (IOC) uses the following terms to the describe the scale and impact of a tsunami (IOC, 2019): Travel time: Time required for the first tsunami wave to propagate from its source to a given point on a coastline. Arrival time: Time of the first maximum of the tsunami waves. Inundation or Inundation-distance: The horizontal distance inland that a tsunami penetrates, generally measured perpendicularly to the shoreline. Inundation (maximum): Maximum horizontal penetration of the tsunami from the shoreline. A maximum inundation is measured for each different coast or harbour affected by the tsunami. Inundation area: Area flooded with water by the tsunami. Inundation height Elevation reached by seawater measured relative to a stated datum such as mean sea level or the sea level at the time of tsunami arrival, at a specified inundation distance. Inundation height is the sum of the flow depth and the local topographic height. Sometimes referred to as tsunami height. Inundation line: Inland limit of wetting measured horizontally from the mean sea level line. The line between living and dead vegetation is sometimes used as a reference. In tsunami science, the landward limit of tsunami run-up. Leading wave: First arriving wave of a tsunami. In some cases, the leading wave produces an initial depression or drop in sea level, and in other cases, an elevation or rise in sea level. When a drop in sea level occurs, sea level recession is observed. Mean height: Average height of a tsunami measured from the trough to the crest after removing the tidal variation. Run-up: Tsunami amplitude: Usually measured on a sea level record, it is (1) the absolute value of the difference between a particular peak or trough of the tsunami and the undisturbed sea level at the time, (2) half the difference between an adjacent peak and trough, corrected for the change of tide between that peak and trough. It is intended to represent the true amplitude of the tsunami wave at some point in the ocean. However, it is often an amplitude modified in some way by the tide gauge response. Tsunami period: Amount of time that a tsunami wave takes to complete a cycle, or one wavelength. Tsunami periods typically range from 5 to 60 minutes. Tsunami period is often measured as the difference between the arrival time of the highest peak and the next one measured on a water level record. Tsunami wavelength: The horizontal distance between similar points on two successive waves measured perpendicular to the crest. The wavelength and the tsunami period give information on the tsunami source. For tsunamis generated by earthquakes, the typical wavelength ranges from 20 to 300 km. For tsunamis generated by landslides, the wavelength is much shorter, ranging from hundreds of meters to tens of kilometers. Meteotsunami: Volcanic eruptions, submarine landslides, and coastal rock falls can also generate tsunamis, as can a large meteorite impacting the ocean. Tsunami-like phenomena generated by meteorological or atmospheric disturbances. For more terms see (IOC, 2019)."
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