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{{short description|System used to detect and warn the public about impending tsunamis}}
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[[File:Tsunami evac sign Seaside Oregon.JPG|thumb|300px|Evacuation route sign in a low-lying coastal area on the West Coast of the United States]]
A '''tsunami warning system''' ('''TWS''') is used to detect [[tsunami]]s 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 (either shore-based tide gauges or [[Deep-ocean Assessment and Reporting of Tsunamis|DART]] buoys) 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 (seismic)|t-wave]] energy (which is earthquake energy trapped in the ocean [[SOFAR channel]]) is indicative of an earthquake's tsunami potential.<ref>Salzberg, 2006</ref>

==History and forecasting==
{{unreferenced section|date=June 2017}}
The first rudimentary system to alert communities of an impending tsunami was attempted in [[Hawaii]] in the 1920s. More advanced systems were developed in the wake of the April 1, 1946 (caused by the [[1946 Aleutian Islands earthquake]]) and May 23, 1960 (caused by the [[1960 Valdivia earthquake]]) tsunamis which caused massive devastation in [[Hilo, Hawaii]].  While tsunamis travel at between 500 and 1,000&nbsp;km/h (around 0.14 and 0.28&nbsp;km/s) in open water, earthquakes can be detected almost at once as [[seismic wave]]s travel with a typical speed of 4&nbsp;km/s (around 14,400&nbsp;km/h).  This gives time for a possible tsunami forecast to be made and warnings to be issued to threatened areas, if warranted.  Until a reliable model is able to predict which earthquakes will produce significant tsunamis, this approach will produce many more false alarms than verified warnings.

==International systems (IS)==

===Pacific Ocean===
[[File:TsunamiHazardSign.svg|right|thumb|Japanese Tsunami warning sign]]
Tsunami warnings ([[Specific Area Message Encoding|SAME]] code:  '''TSW''') for most of the [[Pacific Ocean]] are issued by the [[Pacific Tsunami Warning Center]] (PTWC), operated by the United States [[NOAA]] in [[Ewa Beach, Hawaii]]. NOAA's [[National Tsunami Warning Center]] (NTWC) in [[Palmer, Alaska]] issues warnings for North America, including Alaska, British Columbia, Oregon, California, the Gulf of Mexico, and the East coast. The PTWC was established in 1949, following the 1946 [[Aleutian Island earthquake]] and a tsunami that resulted in 165 casualties on Hawaii and in Alaska; NTWC was founded in 1967. International coordination is achieved through the International Coordination Group for the Tsunami Warning System in the Pacific, established by the [[Intergovernmental Oceanographic Commission]] of [[UNESCO]].<ref>{{cite web |url=http://ioc.unesco.org/itsu/ |title=IOC Oceans &#124; United Nations Educational, Scientific and Cultural Organization |publisher=Ioc.unesco.org |access-date=2018-10-02 |archive-date=2005-05-15 |archive-url=https://web.archive.org/web/20050515085303/http://ioc.unesco.org/itsu/  }}</ref>

===Chile===
In 2005, Chile started to implement the Integrated Plate boundary Observatory Chile (IPOC)<ref>{{cite web| url = http://www.ipoc-network.org/| title = Official website of the Integrated Plate boundary Observatory Chile| access-date = 2020-09-02| archive-date = 2017-07-12| archive-url = https://web.archive.org/web/20170712083530/http://www.ipoc-network.org/| url-status = live}}</ref> which in the following years become a network of 14 multiparameter stations for monitoring the 600-km seismic distance between [[Antofagasta]] and [[Arica]]. Each station was provided with broadband [[seismometer]], [[accelerometer]], [[Global Positioning System|GPS]] [[Antenna (radio)|antenna]]. In four cases, it was installed a short-base [[Tilt-Sensor|tiltmeter]] (pendulum). Some stations were ubicated underground at a depth of 3–4 meters. The network completed the [[Tide gauge|tidal gauge]] of the [[Hydrographic and Oceanographic Service of the Chilean Navy]].<ref name="0956-540X,1July2013" />

The long-base tiltmeters (LBTs) and the STS2 seismometer of the IPOC recorded a series of long-[[Period of a function|period]] signals some days after the [[2010 Maule earthquake]]. The same effect was registered by broadband seismometers of India and Japan some days after the [[2004 Indian Ocean earthquake and tsunami]]. Simulations held in 2013 on historical data highlighted "tiltmeters and broadband seismometers are thus valuable instruments for monitoring tsunamis in complement with tide gauge arrays." In the case of the 2010 Maule earthquake, tilt-sensors observed a discriminating signal "starting 20 min before the arrival time of the tsunami at the nearest point on the coastline."<ref name="0956-540X,1July2013">{{cite journal | doi-access=free | title = Analysis and modelling of tsunami-induced tilt for the 2007, M = 7.6, Tocopilla and the 2010, M = Maule earthquakes, Chile, from long-base tiltmeter and broadband seismometer records |author=F. Boudin |author2=S. Allgeyer |author3=P. Bernard |author4=H. Hébert |author5=M. Olcay |author6=R. Madariaga |author7=M. El-Madani |author8=J.-P. Vilotte |author9=S. Peyrat |author10=A. Nercessian |author11=B. Schurr |author12=M.-F. Esnoult |author13=G. Asch |author14=I. Nunez |author15=M. Kammenthaler | journal = [[Geophysical Journal International]] | volume = 194 | issue = 1 | date = 1 July 2013 | pages = 269–288 | doi = 10.1093/gji/ggt123 | bibcode = 2013GeoJI.194..269B | issn = 0956-540X |hdl=1885/77642 |hdl-access=free }}</ref>

===Indian Ocean (ICG/IOTWMS)===
{{main article|Indian Ocean Tsunami Warning System}}

[[File:Tsunami-warning-centre hikkaduwa sri-lanka.jpg|right|thumb|Tsunami Early Warning Tower board in Hikkaduwa, Sri Lanka]]

After the [[2004 Indian Ocean earthquake|2004 Indian Ocean Tsunami]] which killed almost 250,000 people, a [[United Nations]] conference was held in January 2005 in [[Kobe]], [[Japan]], and decided that as an initial step towards an [[International Early Warning Programme]], the UN should establish an [[Indian Ocean Tsunami Warning System]]. This resulted in a warning system for Indonesia and other affected areas. Indonesia's system fell out of service in 2012 because the detection buoys were no longer operational.{{citation needed|date=March 2024}} Tsunami prediction was then limited to detection of seismic activity, with no system to predict tsunamis based on volcanic eruptions.

Indonesia was hit by tsunamis in [[2018 Sulawesi earthquake and tsunami|September]] and [[2018 Sunda Strait tsunami|December]] 2018. The December 2018 tsunami was caused by a volcano.<ref>{{Cite news|url=https://edition.cnn.com/2018/12/24/asia/indonesia-tsunami-disaster-year-intl/index.html|title=How Indonesia's tsunami warning system failed its citizens again|last=Griffiths|first=James|date=24 December 2018|publisher=CNN|access-date=24 December 2018|archive-date=24 December 2018|archive-url=https://web.archive.org/web/20181224143318/https://edition.cnn.com/2018/12/24/asia/indonesia-tsunami-disaster-year-intl/index.html|url-status=live}}</ref> Sea level sensors were then installed by the Indonesian government to fill the prediction gap.<ref name="Annunziato 2019, p. 68">Annunziato, A, Husrin, S, Prasetya, G. (2019). ANAK KRAKATAU VOLCANO EMERGENCY TSUNAMI EARLY WARNING SYSTEM. ''Science of Tsunami hazards'', pp. 68-95. [https://doaj.org/article/7776a3bb145140fdb10ade3611abd5af link] {{Webarchive|url=https://web.archive.org/web/20210918080439/https://doaj.org/article/7776a3bb145140fdb10ade3611abd5af |date=18 September 2021 }}.</ref>

===North Eastern Atlantic, the Mediterranean and Connected Seas (ICG/NEAMTWS)===
The First United Session of the Inter-governmental Coordination Group for the Tsunami Early Warning and Mitigation System in the North Eastern Atlantic, the Mediterranean and connected Seas (ICG/NEAMTWS), established by the [[Intergovernmental Oceanographic Commission]] of [[UNESCO]] Assembly during its 23rd Session in June 2005, through Resolution XXIII.14, took place in [[Rome]] on 21 and 22 November 2005.

The meeting, hosted by the Government of Italy (the [[Italian Ministry of Foreign Affairs]] and the [[Ministry of the Environment (Italy)|Italian Ministry for the Environment and Protection of Land and Sea]]), was attended by more than 150 participants from 24 countries, 13 organizations and numerous observers.

===Caribbean===

A Caribbean-wide tsunami warning system was planned to be instituted by the year 2010, by representatives of [[Caribbean Community|Caribbean nations]] who met in [[Panama City]] in March 2008. [[Panama]]'s last major tsunami killed 4,500 people in 1882.<ref>{{Cite web|url=https://www.reuters.com/|title=Reuters &#124; Breaking International News & Views|agency=Reuters|access-date=2023-05-13|archive-date=2011-02-24|archive-url=https://web.archive.org/web/20110224005123/http://www.reuters.com/|url-status=live}}</ref> [[Barbados]] has said it will review or test its tsunami protocol in February 2010 as a regional pilot.<ref>{{cite news
  |title=Time right to test disaster awareness system
  |first=Carol |last=Martindale
  |url=http://www.nationnews.com/news/local/tsunami-protocol-in-full-effect-copy-for-web
  |newspaper=[[The Daily Nation (Barbados)|Nation Newspaper]]
  |date=24 January 2010 |access-date=24 January 2010
  |quote=A TSUNAMI PROTOCOL to be tested here next month will help Barbadians be better prepared to deal with natural disasters such as earthquakes. ... Harewood said Barbados was nominated and accepted as the "pilot state" for the tsunami protocol which will be discussed from February 22 to 26.  He said the objective of the Standard Operational Procedure and Communications Protocol, which has been being worked on for the last two years, is to provide more information on what must be done in the event of a tsunami, earthquake or any other major disaster.  He noted that one of the things they would be doing was adopting a general public service announcement through the Government Information Service (GIS) to help increase awareness of tsunamis.
}}</ref>{{update after|2014|7}}

==Regional warning systems==
[[File:1 Tsunamiwarnsystem in Dili.jpg|thumb|Tsunami warning system in [[East Timor]]]]
Regional (or local) warning system centers use [[seismic]] data about nearby recent earthquakes to determine if there is a possible local threat of a tsunami. Such systems are capable of issuing warnings to the general public (via public address systems and sirens) in less than 15 minutes. Although the [[epicenter]] and [[moment magnitude scale|moment magnitude]] of an underwater quake and the probable tsunami arrival times can be quickly calculated, it is almost always impossible to know whether underwater ground shifts have occurred which will result in tsunami waves. As a result, false alarms can occur with these systems, but the disruption is small, which makes sense due to the highly localized nature of these extremely quick warnings, in combination with how difficult it would be for a false alarm to affect more than a small area of the system. Real tsunamis would affect more than just a small portion.
{{Citation needed|date=April 2011}}

===Japan===
[[File:Tsunami evacuation route sign on the road, Kamakura, 2016.jpg|thumb|Evacuation route sign on the pavement in [[Kamakura]], Japan]]
{{See also|Tsunami Warning (Japan)}}
Japan has a nationwide tsunami warning system. The system usually issues the warning minutes after an [[Earthquake Early Warning (Japan)|Earthquake Early Warning]] (EEW) is issued, should there be expected waves.<ref>{{cite web|title=Japan Meteorological Agency – Flow of issuance of information about tsunami and earthquake|url=http://www.data.jma.go.jp/svd/eqev/data/en/guide/info.html|access-date=15 April 2016|archive-date=2 April 2016|archive-url=https://web.archive.org/web/20160402053839/http://www.data.jma.go.jp/svd/eqev/data/en/guide/info.html|url-status=live}}</ref><ref name="2011warning">{{cite web|title=80 Seconds of Warning for Tokyo|url=https://www.technologyreview.com/s/423274/80-seconds-of-warning-for-tokyo/|website=MIT Technology Review|access-date=15 April 2016|archive-date=6 April 2020|archive-url=https://web.archive.org/web/20200406091739/https://www.technologyreview.com/s/423274/80-seconds-of-warning-for-tokyo/|url-status=live}}</ref> The tsunami warning was issued within 3 minutes with the most serious rating on its warning scale during the [[2011 Tōhoku earthquake and tsunami]]; it was rated as a "major tsunami", being at least 3&nbsp;m (9.8&nbsp;ft) high.<ref name="2011warning"/><ref>{{cite web|title=Emergency Warning System Starting Shortly|url=http://www.jma.go.jp/jma/en/Emergency_Warning/Leaflet(Emergency_Warning).pdf|access-date=15 April 2016|archive-date=31 August 2021|archive-url=https://web.archive.org/web/20210831184230/https://www.jma.go.jp/jma/en/Emergency_Warning/Leaflet(Emergency_Warning).pdf|url-status=dead}}</ref> An improved system was unveiled on March 7, 2013, following the 2011 disaster to better assess imminent tsunamis.<ref>{{cite web|title=Leaflet "Start of New Tsunami Warning System Operation"|url=http://www.data.jma.go.jp/svd/eqev/data/en/tsunami/tsunamiwarning-leaflet.pdf|access-date=15 April 2016|archive-date=18 May 2016|archive-url=https://web.archive.org/web/20160518235203/http://www.data.jma.go.jp/svd/eqev/data/en/tsunami/tsunamiwarning-leaflet.pdf|url-status=live}}</ref><ref>{{cite web|title=Tsunami two years on: Japan finally gets warning system that would have saved hundreds of lives|date=9 March 2013|url=https://www.telegraph.co.uk/news/worldnews/asia/japan/9920042/Tsunami-two-years-on-Japan-finally-gets-warning-system-that-would-have-saved-hundreds-of-lives.html|access-date=15 April 2016|archive-date=23 April 2016|archive-url=https://web.archive.org/web/20160423041506/http://www.telegraph.co.uk/news/worldnews/asia/japan/9920042/Tsunami-two-years-on-Japan-finally-gets-warning-system-that-would-have-saved-hundreds-of-lives.html|url-status=live}}</ref>

===India===
India is one of the 5 countries to have the most advanced tsunami warning systems in the world.<ref>{{cite web | url=https://www.undrr.org/news/these-5-countries-have-advanced-tsunami-warning-systems | title=These 5 countries have advanced tsunami warning systems | date=3 November 2021 | access-date=7 September 2022 | archive-date=7 September 2022 | archive-url=https://web.archive.org/web/20220907084938/https://www.undrr.org/news/these-5-countries-have-advanced-tsunami-warning-systems | url-status=live }}</ref> In 2004, right after being hit by an earthquake in Sumatra, a massive tsunami devastated the coasts of India,<ref>{{cite web | url=https://www.britannica.com/event/Indian-Ocean-tsunami-of-2004 | title=Indian Ocean tsunami of 2004 &#124; Facts & Death Toll &#124; Britannica | date=17 November 2023 | access-date=7 September 2022 | archive-date=8 September 2022 | archive-url=https://web.archive.org/web/20220908160813/https://www.britannica.com/event/Indian-Ocean-tsunami-of-2004 | url-status=live }}</ref> prompting the Government of India to set up the [[Indian National Centre for Ocean Information Services|INCOIS]] (Indian National Centre for Ocean Information Services).<ref>{{Cite web|url=https://incois.gov.in/|title=ESSO-INCOIS-Indian National Centre for Ocean Information Services|website=incois.gov.in|access-date=2022-09-07|archive-date=2022-09-06|archive-url=https://web.archive.org/web/20220906061822/https://incois.gov.in/|url-status=live}}</ref> The center is an autonomous organization of the Government of India, under the Ministry of Earth Sciences, located in Pragathi Nagar, Hyderabad, India. This center offers ocean information and advisory services to society, industry, government bodies in areas like Tsunami warning, ocean state forecast, fishing zones and more.<ref>{{Cite web |title=ESSO {{!}} Govt. of India |url=https://tsunami.incois.gov.in/TEWS/ |url-status=live |archive-url=https://web.archive.org/web/20220907084929/https://tsunami.incois.gov.in/TEWS/ |archive-date=2022-09-07 |access-date=2022-09-07}}</ref>

This center receives data from over 35 sea level tide gauges at intervals of 5 minutes.<ref>{{Cite web |title=ESSO {{!}} Govt. of India |url=https://tsunami.incois.gov.in/TEWS/TGMap.jsp |url-status=live |archive-url=https://web.archive.org/web/20221116075836/https://tsunami.incois.gov.in/TEWS/TGMap.jsp |archive-date=2022-11-16 |access-date=2022-09-07}}</ref> Along with this it receives data from wave rider buoys, bottom pressure readers (BPRs) and a network of seismographs that have been installed at various locations in the IOR (Indian Ocean Region). The Indian Tsunami Buoy Type 1 System<ref>{{cite web|url=https://www.niot.res.in/niot1/uploads/technologies_transfer/Type%20-1%20Indian%20Tsunami%20Buoy%20System%20PTN.pdf |title=Indian Tsunami Buoy System Type – 1 |archiveurl=https://web.archive.org/web/20220907084923/https://www.niot.res.in/niot1/uploads/technologies_transfer/Type%20-1%20Indian%20Tsunami%20Buoy%20System%20PTN.pdf|archivedate=2022-09-07}}</ref> consists of 2 units – a surface buoy and a bottom pressure reader (BPR). Communication between BPR and the surface buoy is through acoustic modems and the surface buoys use the INSAT satellite system to communicate readings back to shore stations. The Tsunami warning station collates information from 17 seismic stations of the Indian Meteorological Department (IMD), 10 stations of Wadia Institute of Himalayan Geology (WIHG)<ref>{{cite web|url=https://www.wihg.res.in/|title=Wadia Institute of Himalayan Technology|access-date=2022-09-07|archive-date=2022-09-07|archive-url=https://web.archive.org/web/20220907084927/https://www.wihg.res.in/|url-status=live}}</ref> and more than 300 international stations.
INDOFOS (INDian Ocean FOrecasting System) is a service that forecasts the ocean state and is capable of predicting surface and sub surface features and states of the Indian Ocean.<ref>{{cite web | url=https://incois.gov.in/portal/osf/osf.jsp | title=ESSO-INCOIS-Indian National Centre for Ocean Information Services | access-date=2022-09-07 | archive-date=2022-09-01 | archive-url=https://web.archive.org/web/20220901050347/https://incois.gov.in/portal/osf/osf.jsp | url-status=live }}</ref> These forecasts are made accessible through Information centers, Radio, local digital sign boards, websites, TV channels and subscription services.
Oceansat 2 system is a collection of earth observation satellites operated by ISRO<ref>{{cite web | url=https://www.isro.gov.in/Spacecraft/oceansat-2 | title=Oceansat-2 – ISRO | access-date=2022-09-07 | archive-date=2019-12-11 | archive-url=https://web.archive.org/web/20191211145619/https://www.isro.gov.in/Spacecraft/oceansat-2 | url-status=dead }}</ref> in conjunction with Oceansat ground station that covers an area of 5000&nbsp;km radius around India and is capable of monitoring sea flora and fauna along with oceanic features like meandering patterns, eddies, rings, upwelling and others. Oceansat-2 was successfully deployed to predict the landfall and mitigate the effects of [[Cyclone Phailin]], in October 2013.<ref>{{cite news | url=https://timesofindia.indiatimes.com/india/indias-silent-sentinels-in-space-save-million-lives/articleshow/24069226.cms | title=Oceansat-2 | website=[[The Times of India]] | date=13 October 2013 | access-date=5 October 2022 | archive-date=5 October 2022 | archive-url=https://web.archive.org/web/20221005195759/https://timesofindia.indiatimes.com/india/indias-silent-sentinels-in-space-save-million-lives/articleshow/24069226.cms | url-status=live }}</ref>

==Conveying the warning==
[[File:Okumatsushima tsunami P1130317 rotated.jpg|thumb|Mast with warning system, and sign detailing escape routes, on the coast of [[Okumatsushima]], [[Miyagi Prefecture|Miyagi prefecture]], [[Japan]] (this coast was severely hit by the [[2011 Tōhoku earthquake and tsunami|2011 tsunami]])]]
Detection and prediction of tsunamis is only half the work of the system. Of equal importance is the ability to warn the populations of the areas that will be affected. All tsunami warning systems feature multiple lines of communications (such as [[Cell Broadcast]], [[SMS]], [[e-mail]], [[fax]], [[radio]], texting and [[teleprinter|telex]], often using hardened dedicated systems){{citation needed|date=November 2019}} enabling emergency messages to be sent to the [[emergency service]]s and [[armed forces]], as well to population-alerting systems (e.g. [[siren (noisemaker)|sirens]]) and systems like the [[Emergency Alert System]].<ref>{{cite web |last1=UNESCO |url=http://itic.ioc-unesco.org/index.php?option=com_content&view=category&id=1437&Itemid=1437 |title=Subscribe to Receive International Advisories Through IOC Public Service |website=International Tsunami Information Center |access-date=5 April 2019 |archive-date=6 December 2019 |archive-url=https://web.archive.org/web/20191206021245/http://itic.ioc-unesco.org/index.php?option=com_content&view=category&id=1437&Itemid=1437 |url-status=live }}</ref>

==Shortcomings==
{{unreferenced section|date=June 2017}}
With the speed at which tsunami waves travel through open water, no system can protect against a very sudden tsunami, where the coast in question is too close to the [[epicenter]]. A devastating tsunami occurred off the coast of [[Hokkaidō]] in Japan as a result of [[1993 Okushiri earthquake|an earthquake on July 12, 1993]]. As a result, 202 people on the small island of [[Okushiri, Hokkaido]] lost their lives, and hundreds more were missing or injured.{{citation needed|date=November 2019}} This tsunami struck just three to five minutes after the quake, and most victims were caught while fleeing for higher ground and secure places after surviving the earthquake. This was also the case in [[Aceh]], Indonesia.{{citation needed|date=November 2019}}

While there remains the potential for sudden devastation from a tsunami, warning systems can be effective. For example, if there were a very large [[subduction]] zone [[earthquake]] ([[moment magnitude scale|moment magnitude]] 9.0) off the west coast of the United States, people in [[Japan]], would therefore have more than 12 hours (and likely warnings from warning systems in Hawaii and elsewhere) before any tsunami arrived, giving them some time to evacuate areas likely to be affected.

==See also==
{{portal|Oceans|Tsunamis}}
* [[Deep-ocean Assessment and Reporting of Tsunamis|Deep-ocean Assessment and Reporting of Tsunamis (DART)]]
* [[Disaster risk reduction]]
* [[Pacific Disaster Center]]
* [[SOFAR channel|Sound Fixing and Ranging (SOFAR) channel]]

==References==
{{reflist}}

==External links==
{{Commons category|Tsunami warning systems}}
* [http://www.cwarn.org International Tsunami warnings delivered to mobile phones] {{Webarchive|url=https://web.archive.org/web/20071027065451/http://www.cwarn.org/ |date=2007-10-27 }}
* [http://www.iibc.in/itws A 24/7 mobile SMS Integrated Tsunami Watcher Service] {{Webarchive|url=https://web.archive.org/web/20090415170954/http://www.iibc.in/itws/ |date=2009-04-15 }}
* [http://www.tsunami.noaa.gov/warning_system_works.html How does the Tsunami Warning System Work?] {{Webarchive|url=https://web.archive.org/web/20120319001959/http://www.tsunami.noaa.gov/warning_system_works.html |date=2012-03-19 }}
* [http://ntwc.arh.noaa.gov/ National Tsunami Warning Center]
* [http://www.tsunami.noaa.gov/warnings_forecasts.html NOAA Tsunami Warnings and Forecasts] {{Webarchive|url=https://web.archive.org/web/20110418221600/http://www.tsunami.noaa.gov/warnings_forecasts.html |date=2011-04-18 }}
* [http://espace.library.uq.edu.au/view/UQ:203103 Tsunami Warning Signs on the Enshu Coast of Japan] Shore & Beach, Vol. 78, No. 1, pp.&nbsp;52–54, 2010
* [http://www.bom.gov.au/tsunami/index.shtml Joint Australian Tsunami Warning Centre]

[[Category:Warning systems]]
[[Category:Tsunami|Warning system]]