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Sunda megathrust

Geological feature

Sunda megathrust
Summary

Geological feature

Variation of seismicity with depth across the [[Sunda Trench]] [[subduction]] zone, low-angle part is the Sunda megathrust – [[2007 Bengkulu earthquakes]] mainshock shown by star

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 and Bali before terminating near Australia. It is capable of producing 9.0+ magnitude earthquakes and tsunamis that could reach 30 m (100 ft) high. It is a megathrust, located at a convergent plate boundary where it forms the interface between the overriding Eurasian plate and the subducting Indo-Australian plate. It is one of the most seismogenic structures on Earth, being responsible for many great and giant earthquakes, including the 2004 Indian Ocean earthquake and tsunami 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 segment is much less active and therefore does not have the "megathrust" term associated with it.

Tectonic setting

Plate tectonic setting of Sunda megathrust

The subducting plate consists of two protoplates, the Indian plate and Australian plate. Similarly, the overriding plate consists of two microplates, the Sunda and Burma 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, 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 to about 30° below the coastline of Sumatra.

Earthquakes

Rupture areas for the 1861, 1833 and 2004 earthquakes and area of main shock and aftershocks for the 2005 event, showing similarity to 1861 quake

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, 1833, 1861, 2004, 2005 & 2007), with smaller events occurring at the boundaries between these patches (1935, 1984, 2000 & 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.

Date/Time‡LocationCoordinates--Fatalities--MagnitudeCommentsSources
1797-02-10just north of Siberut, Mentawai islands3008.4See 1797 Sumatra earthquake
1833-11-2550 km NE of North Pagai, Mentawai islands"numerous victims"8.8–9.2 MwSee 1833 Sumatra earthquake
1843-10-05Nias"many killed"≥7.8 MwCaused a devastating tsunami. Maximum intensity XI (Extreme). See 1843 Nias earthquake
1861-02-16Nias9058.5Caused major tsunami. See 1861 Sumatra earthquake.
1907-01-04 05:19just west of Simeulue2,1888.2–8.4Tsunami earthquake that caused a tsunami that devastated Simeulue and Nias, see 1907 Sumatra earthquake
1935-12-28 02:35just west of the Batu Islands7.7See 1935 Sumatra earthquake
1984-11-17 06:49Between Nias and the Batu Islands7.2See 1984 Northern Sumatra earthquake
2000-06-04 16:2870 km NNW of Enggano Island103–1417.9See 2000 Sumatra earthquake
2002-11-02 01:268 km north of Simeulue Regency37.4See 2002 Sumatra earthquake
2004-12-26 00:5850 km north of Simeulue Regency227,8989.2–9.3 MwSee 2004 Indian Ocean earthquake
2005-03-28 16:09Bangkaru, Banyak Islands1,3038.6 Mw (HRV)See 2005 Nias–Simeulue earthquake
2007-09-12 11:10125 km SW of Bengkulu258.4 Mw (HRV)See 2007 Bengkulu earthquakes
2007-09-12 23:49:04 UTC205 km NW of Bengkulu-7.9 Mw (USGS)See 2007 Bengkulu earthquakes
2007-09-13 03:35:26 UTC165 km SSW of Padang-7.0 Mw (USGS)See 2007 Bengkulu earthquakes
2008-02-20 08:36:35 UTC310 km SSE of Banda Aceh37.4 Mw (USGS)See 2008 Simeulue earthquake
2008-02-25 08:36:35 UTC160 km SSW of Padang7.2 Mw (USGS)
2009-09-30 10:16:1045 km WNW of Padang6,2347.6 Mw (USGS)See 2009 Sumatra earthquakes
2010-04-06 22:15:02 UTC215 km SW of Medan62 injuries7.8 Mw (USGS)See 2010 Banyak Islands earthquake
2010-05-09 05:59:42 UTC215 km SSE of Banda Aceh-7.2 Mw (USGS)
2010-10-25 14:42:22 UTC240 km W of Bengkulu435 & 100 missing7.7 Mw (USGS)See 2010 Mentawai earthquake and tsunami

References

References

  1. Chlieh, M.. (2008). "Heterogeneous coupling of the Sumatran megathrust constrained by geodetic and paleogeodetic measurements". Journal of Geophysical Research.
  2. (March 2007). "The Sunda megathrust: past, present and future". Journal of Earthquake and Tsunami.
  3. Monecke, K.. (2008). "A 1,000-year sediment record of tsunami recurrence in northern Sumatra". Nature.
  4. Newcomb, K.R.. (1987). "Seismic history and seismotectonics of the Sunda Arc". Journal of Geophysical Research.
  5. Kerry Sieh*. (2006-08-15). "Sieh, K. 2006. Philosophical Transactions of the Royal Society A, 364 no. 1845 1947–1963". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.
  6. Kalashnikova Tamara. "Destructive historical tsunamis at the western coast of Sumatra, Tsunami Laboratory, Institute of Computational Mathematics and Mathematical Geophysics Siberian Division Russian Academy of Sciences". Tsun.sscc.ru.
  7. "George Pararas-Carayannis, ''The great earthquake and tsunami of 1833 off the coast of Central Sumatra in Indonesia''". Drgeorgepc.com.
  8. "Zachariasen, J., Sieh, K., Taylor, F.W., Edwards, R.L. & Hantoro, W.S. 1999. Submergence and uplift associated with the giant 1833 Sumatran subduction earthquake: Evidence from coral microatolls, Journal of Geophysical Research, Vol. 104, No. B1, Pages 895–919.".
  9. (2013). "Interseismic coupling, stress evolution, and earthquake slip on the Sunda megathrust". [[Geophysical Research Letters]].
  10. (2006). "Earthquake resistant design of structures". PHI Learning Pvt. Ltd..
  11. "Research Group on The December 26, 2004 Earthquake Tsunami Disaster of Indian Ocean". Drs.dpri.kyoto-u.ac.jp.
  12. (2019-03-26). "Reassessment of the 1907 Sumatra "Tsunami Earthquake" Based on Macroseismic, Seismological, and Tsunami Observations, and Modeling". Pure and Applied Geophysics.
  13. IISEENET (Information Network of Earthquake disaster Prevention Technologies). "Search Parameters".
  14. Rivera, L.. (2002). "A Comparative Study of the Sumatran Subduction-Zone Earthquakes of 1935 and 1984". Bulletin of the Seismological Society of America.
  15. "Magnitude 7.4 – SIMEULUE, INDONESIA". United States Geological Survey.
  16. "Magnitude 7.2 – KEPULAUAN MENTAWAI REGION, INDONESIA".
  17. "Magnitude 7.2 – NORTHERN SUMATRA, INDONESIA".
  18. "Magnitude 7.2 – OFF THE WEST COAST OF NORTHERN SUMATRA". United States Geological Survey.
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