Béda révisi "Sunami"

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Ngarapihkeun éjahan, replaced: mangrupakeun → mangrupa, rea → réa, ea → éa (8), eo → éo (2)
m (Ngarapihkeun éjahan, replaced: mangrupakeun → mangrupa, rea → réa, ea → éa (8), eo → éo (2))
[[Gambar:2004 Indian Ocean earthquake Maldives tsunami wave.jpg|thumb|250px|Sunami nu narajang [[Malé]] di [[Maldiva]] [[26 Désémber]] [[2004]].]]
 
'''Sunami''' (éjahan {{IPA|/suˈnɑːmi/}} atawa {{IPA|/tsuˈnɑːmi/}}) hartina runtuyan galura / [[gelombang beungeut sagara|gelombang]] nu dihasilkeun nalika awak [[cai]], misalna [[sagara]] ngalir sacara gancang dina jumlah/[[skala]] anu badag. Sunami ieu biasana mangrupakeunmangrupa balukar ayana [[lini]], [[longsor]], [[gunung bitu]], atawa [[tabrakan météorit]]. Anapon balukarna rupa-rupa, bisa sama sakali teu mangaruhan manusa, tapi bisa ogé ngabalukarkeun musibah anu nelasan ratusan rébu jalma.
 
Istilah ''sunami'' asalna tina [[basa Jepang]] nu hartina ''labuan'' ("tsu", 津) jeung ''gelombang'' ("nami", 波). Sunami téh lain kajadian sub-beungeut di jero [[sagara]]; jangkung gelombang caina ([[amplitudo]]) teu sabaraha, tapi [[panjang gelombang|panjang]] pisan (bisa nepi ka ratusan kilo), sahingga kadang di sagara mah teu pati kabireungeuh.
 
[[Image:Tsunami comic book style.png|right|thumb|Generation of a tsunami]]
Tsunamis can be generated when the [[sea floor]] abruptly deforms and vertically displaces the overlying water. Such large vertical movements of the Earth’s crust can occur at [[plate boundaries]]. [[Subduction]] earthquakes are particularly effective in generating tsunamis. As an Oceanic Plate is subducted beneath a Continental Plate, it sometimes brings down the lip of the Continental with it. Eventually, too much stress is put on the lip and it snaps back, sending shockwaves through the Earth’s crust, causing a tremor under the sea, known as an Undersea Earthquake.
 
Sub-marine [[landslide]]s (which are sometimes triggered by large earthquakes) as well as collapses of volcanic edifices may also disturb the overlying water column as sediment and rocks slide downslope and are redistributed across the sea floor. Similarly, a violent submarine volcanic eruption can uplift the water column and form a tsunami.
 
Waves are formed as the displaced water mass moves under the influence of [[gravity]] to regain its [[equilibrium]] and radiates across the ocean like ripples on a pond.
 
In the 1950s it was discovered that larger tsunamis than previously believed possible could be caused by landslides, explosive volcanic action and [[impact event]]s. These phenomena rapidly displace large volumes of water, as energy from falling debris or expansion is transferred to the water into which the debris falls. Tsunamis caused by these mechanisms, unlike the ocean-wide tsunamis caused by some earthquakes, generally dissipate quickly and rarely affect coastlines distant from the source due to the small area of sea affected. These events can give rise to much larger local shock waves ([[solitons]]), such as the landslide at the head of [[Lituya Bay]] which produced a water wave estimated at 50 – 150 m and reached 524 m up local mountains. However, an extremely large landslide could generate a [[megatsunami]] that might have ocean-wide impacts.
 
[[Image:Tsunami by hokusai 19th century.jpg|thumb|right|300px|There is a common misconception that tsunamis behave like wind-driven waves or swells (with air behind them, as in this celebrated 19th century [[ukiyo-e|woodcut]] by [[Katsushika Hokusai|Hokusai]]). In fact, a tsunami is better understood as a new and suddenly higher sea level, which manifests as a shelf or shelves of water. The leading edge of a tsunami superficially resembles a breaking wave but behaves differently: the rapid rise in sea level, combined with the weight and pressure of the ocean behind it, has far greater force.]]
Often referred to as "tidal waves", a tsunami does not look like the popular impression of "a normal wave only much bigger". Instead it looks rather like an endlessly onrushing tide which forces its way around and through any obstacle. Most of the damage is caused by the huge mass of water behind the initial wave front, as the height of the sea keeps rising fast and floods powerfully into the coastal area. The sheer weight of water is enough to pulverise objects in its path, often reducing buildings to their foundations and scouring exposed ground to the bedrock. Large objects such as ships and boulders can be carried several miles inland before the tsunami subsides.
 
Tsunamis act very differently from typical surf swells: they contain immense energy, propagate at high speeds and can travel great trans-oceanic distances with little overall energy loss. A tsunami can cause damage thousands of kilometres from its origin, so there may be several hours between its creation and its impact on a coast, arriving long after the [[seismic wave]] generated by the originating event arrives. Although the total or overall loss of energy is small, the total energy is spread over a larger and larger circumference as the wave travels. The energy per linear metre in the wave is proportional to the inverse of the distance from the source.{{fact}} (In other words, it decreases linearly with distance.) This is the two-dimensional equivalent of the [[inverse square law]], which is followed by waves which propagate in three dimensions (in a sphere instead of a circle).
 
A single tsunami event may involve a series of waves of varying heights; the set of waves is called a ''train''. In open water, tsunamis have extremely long [[Periodicity|period]]s (the time for the next wave top to pass a point after the previous one), from minutes to hours, and long wavelengths of up to several hundred [[kilometres]]. This is very different from typical wind-generated swells on the ocean, which might have a period of about 10 seconds and a wavelength of 150 [[metre]]s.
 
The actual height of a tsunami wave in open water is often less than one metre. This is often practically unnoticeable to people on ships. Because it has such a large wavelength, the energy of a tsunami mobilizes the entire water column, down to the sea bed. Ocean waves in deep water typically cause water motion to a depth approximately equal to half their wavelength. This means, ocean surface wave motion will only reach down to a depth of a few 100 m or less. Tsunamis, by contrast behave as shallow water waves in the deep ocean (provided their length is at least 20 times the local depth), for which little attenuation of water motion occurs with depth.
 
The wave travels across open ocean at an average speed of 500 mph(''[http://www.pmel.noaa.gov/tsunami/Faq/c_tsunami.htm#2]''). As the wave approaches land, the sea shallows and the wave no longer travels as quickly, so it begins to 'pile-up'; the wave-front becomes steeper and taller, and there is less distance between crests. While a person at the surface of deep water would probably not even notice the tsunami, the wave can increase to a height of six stories or more as it approaches the coastline and compresses. The steepening process is analogous to the cracking of a tapered [[whip]]. As a wave goes down the whip from handle to tip, the same energy is deposited in less and less material, which then moves more violently as it receives this energy.
[[Image:Kamakura_tsunami.jpg|left|200px|thumb|Tsunami warning sign on seawall in [[Kamakura, Kanagawa|Kamakura]], Japan, 2004. In the [[Muromachi period]], a tsunami struck Kamakura, destroying the wooden building that housed the colossal statue of [[Amitabha|Amida]] [[Buddha]] at [[Kotokuin]]. Since that time, the statue has been outdoors.]]
 
In instances where the leading edge of the tsunami is its first peak, succeeding waves can lead to further flooding. Again, being educated about a tsunami is important, to realize that when the water level drops the first time, the danger is not yet over. In a low-lying coastal area, a strong earthquake is a major warning sign that a tsunami may be produced.
 
Regions with a high risk of tsunamis may use [[tsunami warning system]]s to detect tsunamis and warn the general population before the wave reaches land. In some communities on the west coast of the United States, which is prone to Pacific Ocean tsunamis, warning signs advise people where to run in the event of an incoming tsunami. [[Computer model]]s can roughly predict tsunami arrival and impact based on information about the event that triggered it and the shape of the seafloor ([[bathymetry]]) and coastal land ([[topography]]).[http://www.tsunami.noaa.gov/tsunami_story.html]
''See also [[List of natural disasters by death toll#Tsunami|List of historic tsunamis by death toll]].''
 
Tsunamis occur most frequently in the Pacific Ocean, but are a global phenomenon; they are possible wherever large bodies of water are found, including inland lakes, where they can be caused by landslides. Very small tsunamis, non-destructive and undetectable without specialized equipment, occur frequently as a result of minor earthquakes and other events.
 
===Circa 65 million years B.C ===
===1755 - Lisbon, Portugal===
 
Tens of thousands of Portuguese who survived the great '''[[1755 Lisbon earthquake]]''' were killed by a tsunami which followed a half hour later. Many townspeople fled to the waterfront, believing the area safe from fires and from falling debris from aftershocks. Before the great wall of water hit the harbour, waters retreated, revealing lost cargo and forgotten shipwrecks.
 
The earthquake, tsunami, and subsequent fires killed more than a third of Lisbon's pre-quake population of 275,000. Historical records of explorations by [[Vasco da Gama]] and other early navigators were lost, and countless buildings were destroyed (including most examples of Portugal's [[Manueline]] architecture). Europeans of the 18th century struggled to understand the disaster within [[religion|religious]] and [[rationality|rational]] belief systems. Philosophers of the [[The Age of Enlightenment|Enlightenment]], notably [[Voltaire]], wrote about the event. The [[philosophy|philosophical]] concept of the [[sublime (philosophy)|sublime]], as described by philosopher [[Immanuel Kant]] in the ''[[Observations on the Feeling of the Beautiful and Sublime]]'', took inspiration in part from attempts to comprehend the enormity of the Lisbon quake and tsunami.
===1960 - Chilean tsunami===
 
The magnitude-9.5 '''[[Great Chilean Earthquake]]''' was the strongest earthquake ever recorded. Its [[epicentre]] off the coast of South Central [[Chile]], generated one of the most destructive tsunamis of the 20th century.
 
It spread across the entire Pacific Ocean, with waves measuring up to 25 metres high. The first tsunami arrived at [[Hilo, Hawaii]] approximately 14.8 hrs after it originated off the coast of South Central Chile.
 
The highest wave at Hilo Bay was measured at around 10.7 m (35 ft.). 61 lives were lost allegedly due to people's failure to heed warning sirens. When the tsunami hit Onagawa, Japan, almost 22 hours after the quake, the wave height was 3 m above high tide. The number of people killed by the earthquake and subsequent tsunami is estimated to be between 490 and 2,290.
== Rujukan ==
* Dudley, Walter C. & Lee, Min (1988: 1st edition) ''Tsunami!'' ISBN 0-8248-1125-9 [http://www.tsunami.org/references.htm#Books link]
* KenneallyKennéally, Christine (December 30, 2004). "Surviving the Tsunami". ''Slate''. [http://www.slate.com/id/2111608/ link]
* Macey, Richard (January 1, 2005). "The Big Bang that Triggered A Tragedy", ''[[The Sydney Morning Herald]]'', p 11 - quoting Dr Mark LeonardLéonard, seismologist at GeoscienceGéoscience Australia.
* Lambourne, Helen (March 27, 2005). "Tsunami: Anatomy of a disaster". ''[[BBC News]]''. [http://news.bbc.co.uk/1/hi/sci/tech/4381395.stm link]
* abelard.org. ''tsunamis: tsunamis travel fast but not at infinite speed''. Website, retrieved March 29, 2005. [http://www.abelard.org/briefings/tsunami.php link]
* [http://www.whoi.edu/institutes/coi/viewTopic.do?o=read&id=281 Tsunami Information from the Coastal Ocean Institute], [[Woods Hole Oceanographic Institution]]
* [http://www.tsunami.ws Tsunami Forums]
* [http://www.pbs.org/nova/tsunami/ NOVA: Wave That Shook The World] — Site and special report shot within days of the 2004 Indian OceanOcéan tsunami.
* [http://fohn.net/biggest-tsunami/ Biggest Tsunami Countdown] — Description of the five largest historical tsunamis.
* [http://www.tsunami.noaa.gov/ NOAA Tsunami] — General description of tsunamis and the United States agency NOAA's role in [http://www.tsunami.noaa.gov/research_modeling.html Tsunami hazard assessment], [http://www.tsunami.noaa.gov/prepare.html preparedness], [http://www.tsunami.noaa.gov/education.html education], [http://www.tsunami.noaa.gov/warnings_forecasts.html forecasts & warnings], [http://www.tsunami.noaa.gov/responding.html response] and [http://www.tsunami.noaa.gov/research_modeling.html research].
* [http://www.tsunami.org/ Pacific Tsunami Museum]
* [http://walrus.wr.usgs.gov/tsunami/ Tsunamis and Earthquakes]
* [http://tsunami.gov/ Tsunami Centers] — United States National WeatherWéather Service.
* [http://www.sthjournal.org/ ''Science of Tsunami Hazards'' journal]
* [http://www.geohazards.no/ The International Centre for Geohazards (ICG)]
* [http://www.tsunamiterror.info Tsunami: Magnitude of Terror]
* [http://www.cln.org/themes/tsunamis.html General Tsunami Resources]
* [http://www.projectshum.org/NaturalDisasters/tsunami.html Natural Disasters - Tsunami] — GreatGréat researchreséarch site for kids.
* [http://www.envirtech.org/envirtech_tsunameter.htm Envirtech Tsunami Warning System] — Based on seabedséabed seismics and seaséa level gauges.
* [http://www.indianoceandisasterrelief.co.uk Indian Ocean Disaster Relief]
* [http://www.benfieldhrc.org/tsunamis/mega_tsunami_more.htm Benfield Hazard Research - Mega Tsunamis - Cumbre Vieja volcano on the Canary Island of La Palma Risk]
* [http://geology.com/articles/tsunami-geology.shtml What Causes a Tsunami?]
* [http://sciam.com/article.cfm?chanID=sa006&articleID=000CDB86-32E0-13A8-B2E083414B7F0000 Scientific American Magazine (January 2006 Issue) Tsunami: Wave of Change] What we can learnléarn from the Indian OceanOcéan tsunami of December 2004.
* [http://www.jtic.org/ Jakarta Tsunami Information Centre]
 
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