The Sunda megathrust is a fault that extends approximately 5,500 km (3300 mi) from

Myanmar (Burma) Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...

in the north, running along the southwestern side of

Sumatra Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 473,481 km2 (182,812 mi.2), not including adjacent i ...

, to the south of

Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...

and

Bali Bali () is a province of Indonesia and the westernmost of the Lesser Sunda Islands. East of Java and west of Lombok, the province includes the island of Bali and a few smaller neighbouring islands, notably Nusa Penida, Nusa Lembongan, and Nu ...

before terminating near

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. It is a

megathrust 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 earthqu ...

, located at a

convergent plate boundary A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a ...

where it forms the interface between the overriding

Eurasian plate The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent and ...

and the

subducting Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

Indo-Australian plate The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and the surrounding ocean and extends northwest to include the Indian subcontinent and the adjacent waters. It was formed by the fusion of the Indian an ...

. It is one of the most seismogenic structures on Earth, being responsible for many great and giant

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

s, including the

2004 Indian Ocean earthquake An earthquake and a tsunami, known as the Boxing Day Tsunami and, by the scientific community, the Sumatra–Andaman earthquake, occurred at 07:58:53 local time (UTC+7) on 26 December 2004, with an epicentre off the west coast of northern Suma ...

and

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) 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 explo ...

that killed over 227,000 people. The Sunda megathrust can be divided into the ''Andaman Megathrust'', ''Sumatra(n) Megathrust'' and ''Java(n) Megathrust''. The

Sumbawa Sumbawa is an Indonesian island, located in the middle of the Lesser Sunda Islands chain, with Lombok to the west, Flores to the east, and Sumba further to the southeast. Along with Lombok, it forms the province of West Nusa Tenggara, but there ...

segment is much less active and therefore does not have the "megathrust" term associated with it.

Tectonic setting

The subducting plate consists of two protoplates, the

Indian Indian or Indians may refer to: Peoples South Asia * Indian people, people of Indian nationality, or people who have an Indian ancestor ** Non-resident Indian, a citizen of India who has temporarily emigrated to another country * South Asia ...

and

Australian Australian(s) may refer to: Australia * Australia, a country * Australians, citizens of the Commonwealth of Australia ** European Australians ** Anglo-Celtic Australians, Australians descended principally from British colonists ** Aboriginal A ...

plates. Similarly, the overriding plate consists of two microplates, the

Sunda Sunda may refer to: Europe * Sunda, Faroe Islands India * Sunda (asura), an asura brother of Upasunda * Sunda (clan), a clan (gotra) of Jats in Haryana and Rajasthan, India Southeast Asia * Sundanese (disambiguation) ** Sundanese people ...

and

Burma Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...

plates. The relative motion of the subducting and overriding plates varies slightly along strike due to these complexities but is always strongly oblique. The strike-slip component of the oblique convergence is accommodated by displacement on the

Great Sumatran fault The Indonesian island of Sumatra is located in a highly seismic area of the world. In addition to the subduction zone off the west coast of the island, Sumatra also has a large strike-slip fault, the Great Sumatran Fault also known as Semangko ...

, while the dip-slip component is taken up by the Sunda megathrust.

Megathrust geometry

The Sunda megathrust is curviplanar, forming an arc in map view and, at least in Sumatra, increasing in dip from 5°-7° near the trench, then increasing gradually from 15°-20° beneath the

Mentawai Islands Mentawai may refer to: * Mentawai Islands * Mentawai Strait * Mentawai people * Mentawai language The Mentawai language is an Austronesian language, spoken by the Mentawai people of the Mentawai Islands, West Sumatra, Indonesia. Dialects Acco ...

to about 30° below the coastline of Sumatra.

Earthquakes

At this plate boundary, earthquakes occur along the Sunda megathrust and within both the subducting and overriding plates. The largest earthquakes are generated when the megathrust itself ruptures. Studies of both recent and

historical earthquakes Historical earthquakes is a list of significant earthquakes known to have occurred prior to the beginning of the 20th century. As the events listed here occurred before routine instrumental recordings, they rely mainly on the analysis of writte ...

show that the megathrust is segmented. The largest earthquakes occur on separate 'patches' along the megathrust surface ( 1797,

1833 Events January–March * January 3 – Reassertion of British sovereignty over the Falkland Islands (1833), Reassertion of British sovereignty over the Falkland Islands in the South Atlantic. * February 6 – His Royal Highness Prince Otto ...

1861 Statistically, this year is considered the end of the whale oil industry and (in replacement) the beginning of the petroleum oil industry. Events January–March * January 1 ** Benito Juárez captures Mexico City. ** The first steam-p ...

2004 2004 was designated as an International Year of Rice by the United Nations, and the International Year to Commemorate the Struggle Against Slavery and its Abolition (by UNESCO). Events January * January 3 – Flash Airlines Flight 6 ...

2005 File:2005 Events Collage V2.png, From top left, clockwise: Hurricane Katrina in the Gulf of Mexico; the Funeral of Pope John Paul II is held in Vatican City; "Me at the zoo", the first video ever to be uploaded to YouTube; Eris was discovered in ...

2007 File:2007 Events Collage.png, From top left, clockwise: Steve Jobs unveils Apple's first iPhone; TAM Airlines Flight 3054 overruns a runway and crashes into a gas station, killing almost 200 people; Former Pakistani Prime Minister of Pakistan, Pr ...

), with smaller events occurring at the boundaries between these patches (

1935 Events January * January 7 – Italian premier Benito Mussolini and French Foreign Minister Pierre Laval conclude Franco-Italian Agreement of 1935, an agreement, in which each power agrees not to oppose the other's colonial claims. * ...

1984 Events January * January 1 – The Bornean Sultanate of Brunei gains full independence from the United Kingdom, having become a British protectorate in 1888. * January 7 – Brunei becomes the sixth member of the Association of Southeast A ...

2000 File:2000 Events Collage.png, From left, clockwise: Protests against Bush v. Gore after the 2000 United States presidential election; Heads of state meet for the Millennium Summit; The International Space Station in its infant form as seen from ...

2002 File:2002 Events Collage.png, From left, clockwise: The 2002 Winter Olympics are held in Salt Lake City; Queen Elizabeth The Queen Mother and her daughter Princess Margaret, Countess of Snowdon die; East Timor gains East Timor independence, indepe ...

). The rupture area of the 1861 event appears to be very similar to that for the 2005 event, suggesting that it can be regarded as a repeat event. The 2007 event is interpreted to be a partial failure of the rupture area of the 1833 event. The 2004 earthquake ruptured an enormous segment of the megathrust surface. Research into evidence for previous events of this size suggests that they are rare, with two candidate earlier events occurring soon after AD 1290–1400 and AD 780–990. The Java-Bali segment of the megathrust does not appear to be associated with great earthquakes, possibly due to mainly aseismic slip.

List of Sunda megathrust earthquakes

This table lists Sunda Megathrust quakes with magnitudes of 7 or greater, or any known to have caused deaths. Historic records before 2004 are incomplete.

References

{{Earthquakes in Indonesia Sunda megathrust Seismic faults of Oceania Seismic faults of Indonesia