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A megathrust earthquake occurs at subduction zones (destructive plate boundaries), where one tectonic plate
Tectonic Plate

#REDIRECT Plate tectonics...
 is forced under (subducts) another. Due to the shallow dip of the plate boundary, these earthquakes are among the world's largest, with moment magnitudes
Moment magnitude scale

The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The scale was developed in the 1970s to succeed to 1930s-era Richter magnitude scale....
  that can exceed 9.0.

The major subduction zone is associated with the Pacific
Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. Its name is derived from the Latin name Mare Pacificum, "peaceful sea", bestowed upon it by the Portugal explorer Ferdinand Magellan....
 and Indian Ocean
Indian Ocean

The Indian Ocean is the third largest of the world's oceanic divisions, covering about 20% of the water on the Earth's surface. It is bounded on the north by Asia ; on the west by Africa; on the east by Indochina, the Sunda Islands, and Australia; and on the south by the Southern Ocean ....
s and are responsible for the volcanic activity associated with the Ring of Fire
Pacific Ring of Fire

The Pacific Ring of Fire is an area of frequent earthquakes and volcanic eruptions encircling the basin of the Pacific Ocean. In a 40,000 km horseshoe shape, it is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and/or plate movements....
.






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A megathrust earthquake occurs at subduction zones (destructive plate boundaries), where one tectonic plate
Tectonic Plate

#REDIRECT Plate tectonics...
 is forced under (subducts) another. Due to the shallow dip of the plate boundary, these earthquakes are among the world's largest, with moment magnitudes
Moment magnitude scale

The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The scale was developed in the 1970s to succeed to 1930s-era Richter magnitude scale....
  that can exceed 9.0.

The major subduction zone is associated with the Pacific
Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. Its name is derived from the Latin name Mare Pacificum, "peaceful sea", bestowed upon it by the Portugal explorer Ferdinand Magellan....
 and Indian Ocean
Indian Ocean

The Indian Ocean is the third largest of the world's oceanic divisions, covering about 20% of the water on the Earth's surface. It is bounded on the north by Asia ; on the west by Africa; on the east by Indochina, the Sunda Islands, and Australia; and on the south by the Southern Ocean ....
s and are responsible for the volcanic activity associated with the Ring of Fire
Pacific Ring of Fire

The Pacific Ring of Fire is an area of frequent earthquakes and volcanic eruptions encircling the basin of the Pacific Ocean. In a 40,000 km horseshoe shape, it is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and/or plate movements....
. Since these earthquakes deform the ocean floor, they almost always generate a significant tsunami
Tsunami

A is a series of ocean surface wave that is created when a large volume of a body of water, such as an ocean, is rapidly displaced. The Japanese term is literally translated into " harbor wave."...
.

All five earthquakes since 1900 of magnitude 9 or greater have been megathrust earthquakes.

Some examples of megathrust earthquakes are:

  • 365 Crete earthquake
    365 Crete earthquake

    The 365 AD Crete earthquake was an undersea earthquake that occurred at about sunrise on 21 July 365 AD in the Eastern Mediterranean, with an assumed epicentre near Crete....
     (estimated magnitude 8.0+) — African Plate
    African Plate

    The African Plate is a tectonic plate which includes the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges....
     subducting beneath the Eurasian Plate
    Eurasian Plate

    The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia....
    . Generated large tsunami in the eastern Mediterranean Sea
    Mediterranean Sea

    The Mediterranean Sea is a sea or Ocean off the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Europe, on the south by Africa, and on the east by Asia....
     and caused significant vertical displacement in the island of Crete
    Crete

    Crete is the largest of the Greek islands and the List of islands in the Mediterranean largest island in the Mediterranean Sea at 8,336 km? ....
    .
  • 1575 Valdivia earthquake
    1575 Valdivia earthquake

    The 1575 Valdivia earthquake was an earthquake in Chile that caused the subsequent flood of Valdivia, Chile much like the 1960 Valdivia earthquake caused the ensuing Ri?ihuazo flooding....
     (estimated magnitude 8.5) — Nazca Plate
    Nazca Plate

    The Nazca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America....
     subducting beneath the South American Plate
    South American Plate

    The South American Plate is a tectonic plate covering the continent of South America and extending eastward to the Mid-Atlantic Ridge.The easterly side is a divergent boundary with the African Plate forming the southern part of the Mid-Atlantic Ridge....
  • 1700 Cascadia Earthquake
    Cascadia earthquake

    The 1700 Cascadia Earthquake was a moment magnitude scale 8.7 – 9.2 megathrust earthquake that occurred in the Cascadia subduction zone in 1700....
     (estimated magnitude 8.7-9.2) — Juan de Fuca Plate
    Juan de Fuca Plate

    The Juan de Fuca Plate, named after the Juan de Fuca, is a tectonic plate arising from the Juan de Fuca Ridge, and subduction under the northerly portion of the western side of the North American Plate at the Cascadia subduction zone....
     subducting beneath the North American Plate
    North American Plate

    The North American Plate is a tectonic plate covering most of North America, Greenland and part of Siberia. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia....
    , slip length 1000 km (625 mi).
  • 1737 Kamchatka earthquake
    Kamchatka earthquakes

    The Kamchatka earthquakes were a pair of megathrust earthquakes occurring off the coast of the Kamchatka Peninsula, in Russia on October 16, 1737, and on November 4, 1952, with resulting tsunamis following....
     (estimated magnitude 9.0-9.3) — Pacific Plate
    Pacific Plate

    The Pacific Plate is an oceanic tectonic plate beneath the Pacific Ocean.To the north the easterly side is a divergent boundary with the Explorer Plate, the Juan de Fuca Plate and the Gorda Plate forming respectively the Explorer Ridge, the Juan de Fuca Ridge and the Gorda Ridge....
     subducting beneath the Okhotsk Plate
    Okhotsk Plate

    The Okhotsk Plate is a tectonic plate covering the Sea of Okhotsk, the Kamchatka Peninsula, and Eastern Japan. It was formerly considered a part of the North American Plate, but recent studies indicate that it is an independent plate, bounded on the north by the North American Plate....
    , duration 15 minutes, depth 40 km.
  • 1755 Lisbon earthquake
    1755 Lisbon earthquake

    The 1755 Lisbon earthquake, also known as the Great Lisbon Earthquake, took place on November 1, 1755, at around 9:40 in the morning. The earthquake was followed by a tsunami and fires, which caused near-total destruction of Lisbon in Portugal, and adjoining areas....
     (estimated magnitude 9.0) — Hypothesised to be part of a young subduction zone but origin still debated.
  • 1877 Antofagasta (Northern Chile
    Chile

    Chile, officially the Republic of Chile , is a country in South America occupying a long and narrow coastal strip wedged between the Andes mountains and the Pacific Ocean....
    ) earthquake and tsunami (estimated magnitude 8.8) — Nazca Plate
    Nazca Plate

    The Nazca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America....
     subducting beneath the South American Plate
    South American Plate

    The South American Plate is a tectonic plate covering the continent of South America and extending eastward to the Mid-Atlantic Ridge.The easterly side is a divergent boundary with the African Plate forming the southern part of the Mid-Atlantic Ridge....
    .
  • 1946 Nankaido earthquake
    1946 Nankaido earthquake

    The 1946 Nankaido earthquake was a major earthquake in Nankaido, Japan. It occurred on December 20, 1946 at 19:19 UTC. The earthquake was colossal, measuring 8.1 on the moment magnitude scale, and was felt from Northern Honshu to Kyushu....
     (magnitude 8.1 ) — Philippine Plate
    Philippine Plate

    File:Philippine Sea plate.JPGThe Philippine Sea Plate is a tectonic plate beneath the Pacific Ocean to the east of the Philippines. The Philippine Sea Plate comprises oceanic lithosphere that lies beneath the Philippine Sea, and so has been referred to in the scientific literature of the last 50 years as the Philippine Sea Plate....
     subducting beneath the Eurasian Plate
    Eurasian Plate

    The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia....
    .
  • 1950 Nicoya Peninsula (Costa Rica
    Costa Rica

    Costa Rica, officially the Republic of Costa Rica is a country in Central America, bordered by Nicaragua to the north, Panama to the east and south, the Pacific Ocean to the west and south and the Caribbean Sea to the east....
    ) earthquake (magnitude 7.7 ) — Cocos Plate
    Cocos Plate

    The Cocos Plate is an oceanic tectonic plate beneath the Pacific Ocean off the west coast of Central America, named for Cocos Island, which rides upon it....
     subducting beneath the Caribbean Plate
    Caribbean Plate

    The Caribbean Plate is a mostly oceanic crust tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America....
    .
  • 1952 Kamchatka earthquake
    Kamchatka earthquakes

    The Kamchatka earthquakes were a pair of megathrust earthquakes occurring off the coast of the Kamchatka Peninsula, in Russia on October 16, 1737, and on November 4, 1952, with resulting tsunamis following....
     (magnitude 9.0 Richter scale of magnitude) — Pacific Plate
    Pacific Plate

    The Pacific Plate is an oceanic tectonic plate beneath the Pacific Ocean.To the north the easterly side is a divergent boundary with the Explorer Plate, the Juan de Fuca Plate and the Gorda Plate forming respectively the Explorer Ridge, the Juan de Fuca Ridge and the Gorda Ridge....
     subducting beneath the Okhotsk Plate
    Okhotsk Plate

    The Okhotsk Plate is a tectonic plate covering the Sea of Okhotsk, the Kamchatka Peninsula, and Eastern Japan. It was formerly considered a part of the North American Plate, but recent studies indicate that it is an independent plate, bounded on the north by the North American Plate....
    , depth 30 km.
  • 1957 Andreanof Islands earthquake
    1957 Andreanof Islands earthquake

    The 1957 Andreanof Islands Earthquake was a Moment magnitude scale 8.3 megathrust earthquake that took place on March 9, 1957. It was centered at , south of the Andreanof Islands group of the Aleutian Islands in the U.S....
     (magnitude 8.6-9.1 ) — Pacific Plate
    Pacific Plate

    The Pacific Plate is an oceanic tectonic plate beneath the Pacific Ocean.To the north the easterly side is a divergent boundary with the Explorer Plate, the Juan de Fuca Plate and the Gorda Plate forming respectively the Explorer Ridge, the Juan de Fuca Ridge and the Gorda Ridge....
     subducting beneath the North American Plate
    North American Plate

    The North American Plate is a tectonic plate covering most of North America, Greenland and part of Siberia. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia....
    .
  • 1960 Great Chilean Earthquake
    Great Chilean Earthquake

    The 1960 Valdivia earthquake or Great Chilean Earthquake of 22 May, 1960 is to date the most powerful earthquake ever recorded, rating 9.5 on the moment magnitude scale....
     (magnitude 9.5 ) — Nazca Plate
    Nazca Plate

    The Nazca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America....
     subducting beneath the South American Plate
    South American Plate

    The South American Plate is a tectonic plate covering the continent of South America and extending eastward to the Mid-Atlantic Ridge.The easterly side is a divergent boundary with the African Plate forming the southern part of the Mid-Atlantic Ridge....
    , depth 33 km, slip length 1000 km (625 mi), slip width 200 km (125 mi), slip motion 20 m (60 ft).
  • 1964 Good Friday Earthquake
    Good Friday Earthquake

    The 1964 Alaska earthquake, also known as the Great Alaska earthquake, began at 5:36 P.M. AST on Friday, March 27, 1964. Across south-central Alaska, ground fissures, collapsing buildings, and tidal waves directly caused about 131 deaths....
     (magnitude 9.2 ) — Pacific Plate
    Pacific Plate

    The Pacific Plate is an oceanic tectonic plate beneath the Pacific Ocean.To the north the easterly side is a divergent boundary with the Explorer Plate, the Juan de Fuca Plate and the Gorda Plate forming respectively the Explorer Ridge, the Juan de Fuca Ridge and the Gorda Ridge....
     subducting beneath the North American Plate
    North American Plate

    The North American Plate is a tectonic plate covering most of North America, Greenland and part of Siberia. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia....
    , duration 4–5 minutes, depth 25 km, slip length 800 km (500 mi), slip motion 23 m (69 ft).
  • 2004 Indian Ocean earthquake
    2004 Indian Ocean earthquake

    The was an undersea earthquake that occurred at 00:58:53 Coordinated Universal Time on December 26, 2004, with an epicentre off the west coast of Sumatra, Indonesia....
     (magnitude 9.3 ) — India Plate
    India Plate

    The India or Indian Plate is a tectonic plate that was originally a part of the ancient continent of Gondwanaland from which it split off, eventually becoming a major plate....
     subducting beneath the Burma Plate
    Burma Plate

    The Burma Plate is a small tectonic plate or microplate located in Southeast Asia, often considered a part of the larger Eurasian Plate. The Andaman Islands, Nicobar Islands, and northwestern Sumatra are located on the plate....
    , duration 8 - 10 minutes, slip length 1600 km (1000 mi), slip motion ~33 m, total vertical displacement measured by sonar survey is about 40 m in the vicinity of the epicentre and occurred as two separate movements which created two large steep almost vertical cliffs one above the other.


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