The Sunda megathrust is a fault that extends approximately 5,500 km (3300 mi) from Myanmar (Burma) in the north, running along the southwestern side of Sumatra, 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 mos ...

and Bali before terminating near Australia. It is a megathrust, located at a convergent plate boundary 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, fr ...

s, including the 2004 Indian Ocean earthquake 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 exp ...

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

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 th ...

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 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 Ac ...

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

1797 Events January–March * January 3 – The Treaty of Tripoli, a peace treaty between the United States and Ottoman Tripolitania, is signed at Algiers (''see also'' 1796). * January 7 – The parliament of the Cisalpine ...

, 1833,

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 stea ...

, 2004, 2005 & 2007), with smaller events occurring at the boundaries between these patches ( 1935,

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 Southeas ...

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 S ...

& 2002). 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