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 Pacific Tsunami Warning Center (PTWC) 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.
The 1946 Aleutian Islands earthquake occurred near the Aleutian Islands, Alaska on April 1, 1946. The shock measured 8.6, 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 1957 Andreanof Islands earthquake occurred at 04:22 local time on March 9 with a moment magnitude estimated between 8.6 and 9.1 and a maximum Modified Mercalli intensity of VIII (Severe). It occurred south of the Andreanof Islands group, which is part of the Aleutian Islands arc. The event occurred along the Aleutian Trench, the convergent plate boundary that separates the Pacific Plate and the North American plates near Alaska. A basin-wide tsunami followed, with effects felt in Alaska and Hawaii, and strong waves recorded across the Pacific rim. Total losses were around $5 million.
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.
The Central Weather Administration is the government meteorological research and forecasting institution of the Republic of China (Taiwan). In addition to meteorology, the Central Weather Administration also makes astronomical observations, reports on sea conditions, and conducts research into seismology and provides earthquake reports. The Central Weather Administration is headquartered in Taipei City and is administered under the Ministry of Transportation and Communications.
An earthquake occurred on July 17, 2006 at 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 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.
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, and 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 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.
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 2012 Haida Gwaii earthquake occurred just after . 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.
USCGC Kukui (WLB-203) is the third cutter in the Juniper-class 225 ft (69 m) of seagoing buoy tenders and is the third ship to bear the name. She is under the operational control of the Commander of the Seventeenth Coast Guard District and is home-ported in Sitka, Alaska. Her primary area of responsibility is the inland and coastal waters of southeastern Alaska. Kukui conducts heavy lift aids-to-navigation operations, and law enforcement, homeland security, environmental pollution response, and search and rescue as directed.
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 scale, was approximately 280 kilometers (170 mi) southeast of Kodiak and happened at a depth of 25 kilometers (16 mi).
The 2013 Craig, Alaska earthquake struck on January 5, at 12:58 am (UTC–7) near the city of Craig and Hydaburg, on Prince of Wales Island. The Mw 7.5 earthquake came nearly three months after an Mw 7.8 quake struck Haida Gwaii on October 28, in 2012. The quake prompted a regional tsunami warning to British Columbia and Alaska, but it was later cancelled. Due to the remote location of the quake, there were no reports of casualties or damage.
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.
