The Pacific Tsunami Warning Center (PTWC), located on Ford Island, Hawaii, is one of two tsunami warning centers in the United States, covering Hawaii, Guam, American Samoa and the Northern Mariana Islands in the Pacific, as well as Puerto Rico, the U.S. Virgin Islands and the British Virgin Islands in the Caribbean Sea. Other parts of the United States are covered by the National Tsunami Warning Center.
PTWC is also the operational center of the Pacific Tsunami Warning System and issued tsunami warnings for dozens of countries from 1965 to 2014. In October 2014, the authority to issue tsunami warnings was delegated to individual member states. As a result, the center now issues advice rather than official warnings for non-U.S. coastlines, with the exception of the British Virgin Islands.
The PTWC uses seismic data as its starting point, but then takes into account oceanographic data when calculating possible threats. Tide gauges in the area of the earthquake are checked to establish if a tsunami has formed. The center then forecasts the future of the tsunami.
Up until the late 1940s, the United States had no way to warn the public about tsunami threats. After the 1946 Aleutian Islands earthquake, which generated a tsunami and killed more than 170 people in Hawaii, a plan was devised to warn the public of possible tsunami inundation. The facility became operational in 1948 and was called the Seismic Sea Wave Warning System (SSWWS), headquartered at the Coast and Geodetic Survey's seismological observatory in Honolulu, Hawaii. [1]
Initially, the Seismic Sea Wave Warning System covered only the Hawaiian Islands and was limited to teletsunamis (distant events), using data from 4 seismic stations and 9 tide gages. [2] The 1960 Valdivia earthquake and tsunami, which killed thousands of people, led to the establishment of the Pacific Tsunami Warning System under the auspices of UNESCO's Intergovernmental Oceanographic Commission, with the Seismic Sea Wave Warning System as its operational center. As a result, the name of the facility was changed to the Pacific Tsunami Warning Center. [2]
The expanded system became operational in April 1965 but, like its local predecessor, was limited to teletsunamis - tsunamis which are capable of causing damage far away from their source. [3] The system covered all countries of the Pacific Ocean with data from 20 seismic stations around the world and 40 tide stations. [2] [1]
In the aftermath of the 1964 Alaska earthquake and tsunami, which killed 131 people, it was decided to create another warning system to provide timely warnings about local events for coastal areas of Alaska. After Congress approved funding in 1965, the Alaska Regional Tsunami Warning System was launched in September 1967 with observatories in Palmer, Adak and Sitka. At that time, PTWC ended its coverage of Alaska. [4]
The 1975 Hawaii earthquake and tsunami, which killed several people, highlighted the threat of tsunamis caused by nearby events. As a result, PTWC began issuing tsunami warnings for local events near Hawaii. [4]
In 1982, the Alaska Tsunami Warning Center's area of responsibility was enlarged to include California, Oregon and Washington, as well as British Columbia in Canada, but only for earthquakes in the vicinity of the West Coast. PTWC continued to provide coverage of teletsunamis. The Alaska center's responsibilities were expanded in 1996 to include all Pacific-wide sources, after which it became known as the West Coast/Alaska Tsunami Warning Center (WCATWC). As a result, PTWC's area of responsibility was further reduced. [4]
On December 1, 2001, the PTWC was re-dedicated as the Richard H. Hagemeyer Pacific Tsunami Warning Center, in honor of the former U.S. Tsunami Program Manager and National Weather Service Pacific Region Director who managed the center for many years. [4]
In 2005, in the aftermath of the 2004 Indian Ocean earthquake and tsunami, the Pacific Tsunami Warning Center's responsibilities were expanded to include tsunami guidance for the Indian Ocean, the South China Sea and the Caribbean Sea, though its authority to issue warnings was limited to Puerto Rico and the U.S. Virgin Islands. For all other areas, the decision to issue tsunami warnings was left to individual countries.
The responsibility for Puerto Rico and the U.S. Virgin Islands was passed to the West Coast/Alaska Tsunami Warning Center in June 2007, while PTWC continued to issue advice for other parts of the Caribbean Sea. In 2013, the West Coast/Alaska Tsunami Warning Center became known as the National Tsunami Warning Center. [4]
PTWC discontinued its messages for the Indian Ocean in 2013 after regional tsunami warning centers were opened in Australia, India and Indonesia. [5]
In October 2014, the authority to issue official tsunami warnings for coastlines in the Pacific was delegated to individual member states. This happened because warnings and watches issued by PTWC caused confusion when they conflicted with a country's independently derived level of alert. As a result, the center now issues advice rather than official warnings for all non-U.S. coastlines, with the exception of the British Virgin Islands. [6]
In 2015, the annual operating cost of the Pacific Tsunami Warning System was estimated to be between 50 and 80 million U.S. dollars. [2]
In April 2017, the responsibility for Puerto Rico and the U.S. Virgin Islands returned to PTWC, along with the British Virgin Islands, to consolidate Caribbean responsibilities under one warning center. [7]
As of 2023, the Pacific Tsunami Warning System has access to about 600 high-quality seismic stations around the world and about 500 coastal and deep-ocean sea level stations. It has 46 member states: Brunei, Cambodia, Canada, Chile (including Easter Island and the Juan Fernández Islands), China (which is considered to include Hong Kong and Macau), Colombia, Costa Rica, East Timor, North Korea, Ecuador (including the Galapagos Islands), El Salvador, Guatemala, Honduras, Indonesia, Japan, Malaysia, Mexico, Nicaragua, Panama, Peru, Philippines, South Korea, Russia, Singapore, Thailand, United States (including Guam, Northern Mariana Islands, and the Minor Outlying Islands), Vietnam, Australia (including Norfolk Island), Cook Islands, Fiji, France (including French Polynesia, New Caledonia and Wallis and Futuna), Kiribati (including the Gilbert Islands, the Phoenix Islands and Kiritimati), the Marshall Islands (including Kwajalein Atoll and Majuro), the Federated States of Micronesia, Nauru, New Zealand (including the Kermadec Islands), Niue, Palau, Papua New Guinea, Samoa, the Solomon Islands, Tokelau, Tonga, Tuvalu, the United Kingdom (including the Pitcairn Islands), and Vanuatu. [8]
Status | Regions |
---|---|
Tsunami warning authority | Hawaii, American Samoa, Guam, Northern Mariana Islands, Puerto Rico, U.S. Virgin Islands, British Virgin Islands |
Guidance only | All other parts of the Pacific Ocean and the Caribbean Sea |
Discontinued | Indian Ocean (2005–2013), South China Sea |
Official tsunami warnings and watches are limited to U.S. coastlines, with the exception of the British Virgin Islands. PTWC messages for other regions do not include alerts, but rather advice, as the authority to issue tsunami warnings was delegated to member states in 2014 to avoid confusion among the public. [6]
Alert Level | Potential Hazard | Public Action |
---|---|---|
Warning | Dangerous coastal flooding and powerful currents | Move to high ground or inland |
Advisory | Strong currents and waves dangerous to those in or very near water | Stay out of water, away from beaches and waterways |
Watch | Not yet known | Stay tuned for more information, be prepared to act |
Information | No threat or very distant event for which hazard has not yet been determined | No action needed at this time |
Alert Level | Potential Hazard | Public Action |
---|---|---|
Threat | Dangerous coastal flooding and/or strong and unusual currents dangerous to those in or very near the water | Seek more information, follow instructions from national and local authorities |
Information | Minor waves at most | No action suggested other than normal caution around the sea |
The alert levels below were retired on October 1, 2014.
Alert Level | Description |
---|---|
Warning | Widespread, dangerous coastal flooding accompanied by powerful currents are possible |
Watch | An event may impact the watch area at a later time |
Information | Earthquake notification. In some cases it may caution about the possibility of a local tsunami |
Alert Level | Description |
---|---|
Warning | Widespread, dangerous coastal flooding accompanied by powerful currents are possible |
Watch | An event may impact the watch area at a later time |
Advisory | Strong currents or waves are possible |
Information | Earthquake notification. In some cases it may caution about the possibility of a local tsunami |
Alert Level | Description |
---|---|
Watch | Destructive tsunami possible |
Information | Earthquake notification. In some cases it may caution about the possibility of a local tsunami |
![]() | This section needs to be updated.(August 2023) |
Local populations in the United States of America receive tsunami information through radio and television receivers connected to the Emergency Alert System, and in some places (such as Hawaii) civil defense sirens and roving loudspeaker broadcasts from police vehicles. The public can subscribe to the RSS feed or email alerts from the PTWC web site, [13] and the UNESCO site. [14] Email and text messages are also available from the USGS Earthquake Notification Service [15] which includes tsunami alerts.
In 1995, NOAA began developing the Deep-ocean Assessment and Reporting of Tsunamis (DART) system. By 2001, an array of six stations had been deployed in the Pacific Ocean. [16]
Beginning in 2005, as a result of the tsunami caused by the 2004 Indian Ocean earthquake, plans were announced to add 32 more DART buoys to be operational by mid-2007. [17]
These stations give detailed information about tsunamis while they are still far off shore. Each station consists of a sea-bed bottom pressure recorder (at a depth of 1000–6000 m) which detects the passage of a tsunami and transmits the data to a surface buoy via acoustic modem. The surface buoy then radios the information to the PTWC via the GOES satellite system. The bottom pressure recorder lasts for two years while the surface buoy is replaced every year. The system has considerably improved the forecasting and warning of tsunamis in the Pacific Ocean.
A tsunami 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. Earthquakes, volcanic eruptions and other underwater explosions above or below water all have the potential to generate a tsunami. Unlike normal ocean waves, which are generated by wind, or tides, which are in turn generated by the gravitational pull of the Moon and the Sun, a tsunami is generated by the displacement of water from a large event.
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 1946 Aleutian Islands earthquake occurred near the Aleutian Islands, Alaska on April 1, 1946. The shock measured 8.6, Mt 9.3 or 7.4. It had a maximum Mercalli intensity of VI (Strong). It resulted in 165–173 casualties and over US $26 million in damage. The seafloor along the fault was elevated, triggering a Pacific-wide tsunami with multiple destructive waves at heights ranging from 45–138 ft (14–42 m). The tsunami obliterated the Scotch Cap Lighthouse on Unimak Island, Alaska among others, and killed all five lighthouse keepers. Despite the destruction to the Aleutian Island Unimak, the tsunami had almost an imperceptible effect on the Alaskan mainland.
Deep-ocean Assessment and Reporting of Tsunamis (DART) is a component of an enhanced tsunami warning system.
The Indian Ocean Tsunami Warning System was set up to provide warning to inhabitants of nations bordering the Indian Ocean of approaching tsunamis. The tsunami warning system has been in use since the mid-2000s.
The Aleutian Trench is an oceanic trench along a convergent plate boundary which runs along the southern coastline of Alaska and the Aleutian islands. The trench extends for 3,400 kilometres (2,100 mi) from a triple junction in the west with the Ulakhan Fault and the northern end of the Kuril–Kamchatka Trench, to a junction with the northern end of the Queen Charlotte Fault system in the east. It is classified as a "marginal trench" in the east as it runs along the margin of the continent. The subduction along the trench gives rise to the Aleutian Arc, a volcanic island arc, where it runs through the open sea west of the Alaska Peninsula. As a convergent plate boundary, the trench forms part of the boundary between two tectonic plates. Here, the Pacific Plate is being subducted under the North American Plate at a dip angle of nearly 45°. The rate of closure is 7.5 centimetres (3 in) per year.
The National Data Buoy Center (NDBC) is a part of the National Oceanic and Atmospheric Administration's (NOAA) National Weather Service (NWS). NDBC designs, develops, operates, and maintains a network of data collecting buoys and coastal stations. The NDBC is located in southern Mississippi as a tenant at the John C. Stennis Space Center, a National Aeronautics and Space Administration (NASA) facility.
An earthquake occurred on July 17, 2006 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.
The 2007 Solomon Islands earthquake took place on 2 April 2007, near the provincial capital of Gizo on Ghizo Island, in the Solomon Islands. Its magnitude was estimated at 8.1 on the Mw scale, and 7.8 on the Ms scale. The tsunami that followed the earthquake killed 52 people. According to the USGS, the earthquake was recorded around 7:39:56 a.m. local time (UTC+11). The focus was 10 km (6 mi) deep and 40 km (25 mi) south southeast of Gizo township on New Georgia Islands in Western Province. There were numerous aftershocks, the largest of which had a magnitude of 6.2.
The September 2007 Sumatra earthquakes were a series of megathrust earthquakes that struck the Sunda Trench off the coast of Sumatra, Indonesia, with three of magnitude 7 or greater. A series of tsunami bulletins was issued for the area. The most powerful of the series had a magnitude of 8.5, which makes it in the top 20 of the largest earthquakes ever recorded on a seismograph.
The National Warning System (NAWAS) is an automated telephone system used to convey warnings to United States-based federal, state and local governments, as well as the military and civilian population. The original mission of NAWAS was to warn of an imminent enemy attack or an actual accidental missile launch upon the United States. NAWAS still supports this mission but the emphasis is on natural and technological disasters. Organizations are able to disseminate and coordinate emergency alerts and warning messages through NAWAS and other public systems by means of the Integrated Public Alert and Warning System.
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, 2004 Indian Ocean earthquake, 2011 Tohoku earthquake, and the 2021 South Sandwich Islands earthquakes.
The 2010 Chile earthquake and tsunami occurred off the coast of central Chile on Saturday, 27 February at 03:34:12 local time, having a magnitude of 8.8 on the moment magnitude scale, with intense shaking lasting for about three minutes. It was felt strongly in six Chilean regions that together make up about 80 percent of the country's population. According to the United States Geological Survey (USGS) the cities experiencing the strongest shaking—VIII (Severe) on the Mercalli intensity scale (MM)—were Concepción, Arauco, and Coronel. According to Chile's Seismological Service, Concepción experienced the strongest shaking at MM IX (Violent). The earthquake was felt in the capital Santiago at MM VII or MM VIII. Tremors were felt in many Argentine cities, including Buenos Aires, Córdoba, Mendoza, and La Rioja. Tremors were felt as far north as the city of Ica in southern Peru. It is the largest earthquake to hit Chile since the 1960 Valdivia earthquake.
Although National Oceanic and Atmospheric Administration (NOAA) scientists at the Pacific Tsunami Warning Center (PTWC) in Hawaii eventually issued warnings of a possible tsunami from the large earthquake off Sumatra, the waves outran notification systems at jet speeds of 500 mph (804 km/h), catching hundreds of thousands of people unaware. The following is a timeline of the 2004 Indian Ocean earthquake. All times are Coordinated Universal Time (UTC), on Sunday, 26 December 2004.
The National Tsunami Warning Center (NTWC) is one of two tsunami warning centers in the United States, covering all coastal regions of the United States and Canada, except Hawaii, Guam, the Northern Mariana Islands, Puerto Rico and the U.S. Virgin Islands. Until 2013, it was known as the West Coast and Alaska Tsunami Warning Center.
The 2012 Indian Ocean earthquakes were magnitude 8.6 and 8.2 Mw undersea earthquakes that struck near the Indonesian province of Aceh on 11 April at 15:38 local time. Initially, authorities feared that the initial earthquake would cause a tsunami and warnings were issued across the Indian Ocean; however, these warnings were subsequently cancelled. These were unusually strong intraplate earthquakes and the largest strike-slip earthquake ever recorded.
The 2012 Haida Gwaii earthquake occurred just after 8:04 p.m. PDT on October 27. The shock had a moment magnitude of 7.8 and a maximum Mercalli Intensity of V (Moderate). The earthquake's epicentre was on Moresby Island of the Haida Gwaii archipelago. This was the second largest Canadian earthquake ever recorded by a seismometer, after the 1949 Queen Charlotte Islands earthquake, about 135 kilometres (84 mi) away. One person died due to a car crash related to the tsunami in Oahu, Hawaii.
On January 23, 2018, at 00:31 AKST, an earthquake occurred in the Gulf of Alaska near Kodiak Island. The earthquake, measured at 7.9 on the Mw scale, was approximately 280 kilometers (170 mi) southeast of Kodiak and happened at a depth of 25 kilometers (16 mi).
An earthquake occurred off the coast of the Alaska Peninsula on July 28, 2021, at 10:15 p.m. local time. The large megathrust earthquake had a moment magnitude of 8.2 according to the United States Geological Survey (USGS). A tsunami warning was issued by the National Oceanic and Atmospheric Administration (NOAA) but later cancelled. The mainshock was followed by a number of aftershocks, including three that were of magnitude 5.9, 6.1 and 6.9 respectively.
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