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 generated by the gravitational pull of the Moon and the Sun, a tsunami is generated by the displacement of water.
The 2004 Indian Ocean earthquake and tsunami occurred at 07:58:53 in local time (UTC+7) on 26 December, with an epicentre off the west coast of northern Sumatra, Indonesia. It was an undersea megathrust earthquake that registered a magnitude of 9.1–9.3 , reaching a Mercalli intensity up to IX in certain areas. The earthquake was caused by a rupture along the fault between the Burma Plate and the Indian Plate.
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 that are operated by NOAA in the United States. Headquartered on Ford Island, HI, the PTWC is part of an international tsunami warning system (TWS) program and serves as the operational center for TWS of the Pacific issuing bulletins and warnings to participating members and other nations in the Pacific Ocean area of responsibility. It is also the regional (local) warning center for the State of Hawaii. The other tsunami warning center is the National Tsunami Warning Center (NTWC) in Palmer, Alaska, serving all coastal regions of Canada and the United States except Hawaii, the Caribbean Sea and the Gulf of Mexico.
Deep-ocean Assessment and Reporting of Tsunamis (DART) is a component of an enhanced tsunami warning system.
The 2005 Nias–Simeulue earthquake occurred on 28 March off the west coast of northern Sumatra, Indonesia. At least 915 people were killed, mostly on the island of Nias. The event caused panic in the region, which had already been devastated by the massive tsunami triggered by the 2004 Indian Ocean earthquake, but this earthquake generated a relatively small tsunami that caused limited damage. It was the third most powerful earthquake since 1965 in Indonesia.
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 8.4, which makes it in the top 20 of the largest earthquakes ever recorded on a seismograph.
The 2007 Tocopilla earthquake occurred on November 14 at . Its epicenter was located between Quillagua and Tocopilla, affecting the Tarapacá and the Antofagasta regions in northern Chile. The earthquake had a moment magnitude of 7.7 and lasted about 3 minutes and 35 seconds. Seventeen aftershocks of magnitude greater than 5.3, including one of magnitude 7.1 and two others of magnitude 6.3 or higher, were recorded. The Pacific Tsunami Warning Center issued a tsunami warning, stating a tsunami had been generated; after one hour, this warning was cancelled. The earthquake was felt from Santiago, 1,245 km south from the epicenter, to La Paz, about 700 km north-northeast.
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, and 2004 Indian Ocean earthquake.
The 2010 Chile earthquake 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.
The 2011 earthquake off the Pacific coast of Tōhoku was a magnitude 9.0–9.1 (Mw) undersea megathrust earthquake off the coast of Japan that occurred at 14:46 JST on Friday 11 March 2011, with the epicenter approximately 70 kilometers (43 mi) east of the Oshika Peninsula of Tōhoku and the hypocenter at an underwater depth of approximately 29 km (18 mi).
The National Tsunami Warning Center (NTWC) forms part of an international tsunami warning system (TWS). It serves as the operations center for all coastal regions of Canada and the United States, except Hawaii, the Caribbean, and the Gulf of Mexico. Headquartered in Palmer, Alaska, it is operated by the National Oceanic and Atmospheric Administration (NOAA).
The April 2011 Miyagi earthquake occurred off the coast of Miyagi Prefecture, approximately 66 kilometres (41 mi) east of Sendai, Japan. The 7.1 thrust earthquake was classified as an aftershock of the March 11 Tōhoku earthquake, and occurred at 23:32 JST (14:32 UTC) on Thursday, 7 April 2011.
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 2013 Solomon Islands earthquake struck northeast of Australia on 6 February with a moment magnitude of 8.0 and a maximum Mercalli intensity of VIII (Severe). Its epicenter was the Solomon Islands, at the boundaries of the Australian and Pacific tectonic plates, causing local evacuations and a tsunami of 1.5 m (4.9 ft) and killing at least nine people.
The 2016 Sumatra earthquake was a 7.8 magnitude earthquake which struck on 2 March 2016 in the Indian Ocean, approximately 800 kilometers southwest of Sumatra in Indonesia. Tsunami warnings were issued for Indonesia and Australia, but were withdrawn two hours later. Heronimus Guru, the National Meteorological Agency's deputy head of operations, initially stated that "there are some who have died", without citing an official death toll; however, it is now known that there were no deaths directly related to the earthquake.
The 2016 Fukushima earthquake struck Japan with a moment magnitude of 6.9 east-southeast of Namie, Fukushima Prefecture at 05:59 JST on November 22, at a depth of 11.4 km (7.1 mi). The shock had a maximum intensity of VII (Very strong) on the Mercalli scale. The earthquake was initially reported as a 7.3 magnitude by Japan Meteorological Agency, which was later upgraded to a 7.4, while the United States Geological Survey and GFZ Potsdam determined a magnitude of 6.9. It was reported to be an aftershock of the 2011 earthquake.
The 1907 Sumatra earthquake occurred on January 4 at 05:19:12 UTC. The estimated magnitude is 7.5–8.0 , with an epicentre close to Simeulue, off Sumatra. It triggered a widespread and damaging tsunami that caused at least 2,188 deaths. The low observed intensity compared to the size of the tsunami has led to its interpretation as a tsunami earthquake. Higher levels of shaking observed on Nias are attributed to a large aftershock, less than an hour later. The tsunami gave rise to the S'mong legend, which is credited with saving many lives during the 2004 earthquake.
The October 2020 Simeonof earthquake was a magnitude 7.6 earthquake that struck 97 km south southeast from the city of Sand Point, Alaska. It came almost three months after a magnitude 7.8 struck the same region. This earthquake is considered an aftershock of the July event. No damage was reported immediately following the earthquake.
On 9 December 2016 at 4:38 a.m. local time, the Solomon Islands region was rocked by an Mww 7.8 earthquake, centered 30 km off San Cristobal Island, about 61 km southwest of Kirakira, the capital of Makira-Ulawa Province. Initially registering magnitude 8.0, later downgraded to 7.8, the temblor prompted tsunami warnings that kept countries surrounding the Coral, Tasman and Solomon Sea on high alert, but was later cancelled. A large aftershock of magnitude 6.9 occurred shortly afterwards. This earthquake was largely felt, waking many residents who later ran to high ground for fears of a potential tsunami. The earthquake killed a child and affected some 34,000 people in Makira, South Malaita and Guadalcanal Island where many had lost their homes or had no access to basic needs. Earthquakes are common in this region, with little or no fatalities. This earthquake is tied with three other magnitude 7.8 earthquakes for the second largest earthquake of 2016. On December 17, the Solomon Islands would be rattled again by a 7.9 magnitude earthquake, this time 54 km east of Taron, Papua New Guinea.
