Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthquakes are the planet's most powerful, with moment magnitudes (Mw) that can exceed 9.0. Since 1900, all earthquakes of magnitude 9.0 or greater have been megathrust earthquakes.
The 1995 Antofagasta earthquake occurred on July 30 at 05:11 UTC with a moment magnitude of 8.0 and a maximum Mercalli intensity of VII. The Antofagasta Region in Chile was affected by a moderate tsunami, with three people killed, 58 or 59 injured, and around 600 homeless. Total damage from the earthquake and tsunami amounted to $1.791 million.
The 1797 Sumatra earthquake occurred at 22:00 local time on 10 February. It was the first in a series of great earthquakes that ruptured part of the Sumatran segment of the Sunda megathrust. It caused a damaging tsunami that was particularly severe near Padang, where a 150–200 t English ship was driven 1 km (0.62 mi) inland up the Arau River.
The 1881 Nicobar Islands earthquake occurred at about 07:49 local time on 31 December, with an epicentre beneath Car Nicobar. It occurred as two separate ruptures, the largest of which had an estimated magnitude of 7.9 on the moment magnitude scale and triggered a tsunami that was observed around the Bay of Bengal. It is probably the earliest earthquake for which rupture parameters have been estimated instrumentally.
The 1877 Iquique earthquake occurred at 21:16 local time on 9 May. It had a magnitude of 8.5 on the surface-wave magnitude scale. Other estimates of its magnitude have been as high as 8.9 and 9.0 . It had a maximum intensity of XI (Extreme) on the Mercalli intensity scale and triggered a devastating tsunami. A total of 2,385 people died, mainly in Fiji from the tsunami.
The 1944 Tōnankai earthquake occurred at 13:35 local time on 7 December. It had an estimated magnitude of 8.1 on the moment magnitude scale and a maximum felt intensity of greater than 5 Shindo. It triggered a large tsunami that caused serious damage along the coast of Wakayama Prefecture and the Tōkai region. Together, the earthquake and tsunami caused 3,358 casualties.
The 1968 Hyūga-nada earthquake occurred on April 1 at . The earthquake had a magnitude of 7.5, and the epicenter was located in Hyūga-nada Sea, off the islands of Kyushu and Shikoku, Japan. The magnitude of this earthquake was also given as 7.5. A tsunami was observed. One person was killed, and 22 people were reported injured. The intensity reached shindo 5 in Miyazaki and Kōchi.
In seismology, a tsunami earthquake is an earthquake which triggers a tsunami of significantly greater magnitude, as measured by shorter-period seismic waves. The term was introduced by Japanese seismologist Hiroo Kanamori in 1972. Such events are a result of relatively slow rupture velocities. They are particularly dangerous as a large tsunami may arrive at a coastline with little or no warning.
The 1746 Lima–Callao earthquake occurred at on 28 October with a moment magnitude of 8.6–8.8 and a maximum Mercalli intensity of XI (Extreme). The epicenter was located about 90 km (56 mi) north-northwest of the capital Lima, which was almost completely destroyed, and the subsequent tsunami devastated the port city of Callao. It was the deadliest earthquake in Peru's history prior to the 1970 earthquake.
The 1942 Peru earthquake occurred on August 24 at and was located near the border of the departments of Ica and Arequipa, Peru. It had a magnitude of 8.2 or 8.4.
The 1839 Martinique earthquake occurred on the morning of January 11 with an estimated magnitude of 7.8 Ms , the largest in the Lesser Antilles since 1690. The maximum intensity of this earthquake was assigned IX on both the Mercalli and MSK intensity scales, which left the cities of Saint-Pierre and Fort Royal almost completely destroyed. Estimation on the number of human losses varies from 390 to 4,000 making this one of the deadliest earthquakes in the Caribbean.
On January 30, 1973, at 15:01 (UTC–6), a magnitude 7.6 earthquake struck 35.3 km (21.9 mi) beneath the Sierra Madre del Sur range in the Mexican states of Colima, Jalisco and Michoacán. On the Mercalli intensity scale, the earthquake reached a maximum intensity of X (Extreme), causing serious damage in the region. At least 56 people were killed and about 390 were injured. The event is commonly referred to as the Colima earthquake.
The Nemuro-Oki earthquake in scientific literature, occurred on June 17 at 12:55 local time. It struck with an epicenter just off the Nemuro Peninsula in northern Hokkaidō, Japan. It measured 7.8–7.9 on the moment magnitude scale (Mw ), 8.1 on the tsunami magnitude scale (Mt ) and 7.4 on the Japan Meteorological Agency magnitude scale (MJMA ).
An earthquake occurred on 26 August 2012 at 22:37 local time. The earthquake located off the coast of El Salvador measured 7.3 on the moment magnitude scale and had a focal depth of 16.0 kilometres (10 mi). No deaths were reported, however more than 40 people were injured when they were caught in a tsunami generated by the earthquake. Waves from the tsunami were unusually large for an earthquake of this size. The large waves were attributed to the earthquake's unique rupture characteristic. In addition to the absence of fatalities, damage caused by the earthquake and tsunami was minimal as a result of the sparse population around the affected region and the slow rupture characteristic of the event.
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.
The 1979 Petatlán earthquake, also known as the IBERO earthquake occurred on March 14 at 05:07 local time in the Mexican state of Guerrero. The earthquake had a surface-wave magnitude of Ms 7.6 or moment magnitude of Mw 7.4 and maximum Modified Mercalli intensity of VIII (Severe). The epicenter, onshore, was located 12 km south southeast of Vallecitos de Zaragoza.
During April 1819, the area around Copiapó in northern Chile was struck by a sequence of earthquakes over a period of several days. The largest of these earthquakes occurred on 11 April at about 15:00 local time, with an estimated magnitude of 8.5. The other two events, on 3 April between 08:00 and 09:00 local time and on 4 April at 16:00 local time, are interpreted as foreshocks to the mainshock on 11 April. The mainshock triggered a tsunami that affected 800 km of coastline and was also recorded at Hawaii. The city of Copiapó was devastated.
The 1950 Calama earthquake occurred near the Argentina–Chile border with an epicenter near Calama, Chile in the Atacama Desert on December 9. The event had a hypocenter depth of 113.9 km, beneath the Caichinque volcanic complex. It measured magnitude Mw 8.2 on the moment magnitude scale, making it the largest intermediate depth earthquake ever recorded on Chilean soil. One person was killed and an unspecified number of people were injured in Calama.
The 1843 Nias earthquake off the northern coast of Sumatra, Indonesia caused severe damage when it triggered a tsunami along the coastline. The earthquake with a moment magnitude (Mw ) of 7.8 lasted nine minutes, collapsing many homes in Sumatra and Nias. It was assigned a maximum modified Mercalli intensity of XI (Extreme).
The 1979 Saint Elias earthquake affected Alaska at 12:27 AKST on 28 February. The thrust-faulting 7.5 earthquake had an epicenter in the Granite Mountains. Though the maximum recorded Modified Mercalli intensity was VII, damage was minimal and there were no casualties due to the remoteness of the faulting. Damage also extended across the border in parts of Yukon, Canada.
