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 Fault, running the entire length of the island. This fault zone accommodates most of the strike-slip motion associated with the oblique convergence between the Indo-Australian and Eurasian plates.[1] The fault ends in the north just below the city of Banda Aceh, which was devastated in the 2004 Indian Ocean earthquake. After the December 2004 earthquake, pressure on the Great Sumatran Fault has increased tremendously, especially in the north.
Geologic Significance
The Great Sumatran Fault is part of the system where strain partitioning was first described in plate tectonics.[2] The convergence between the Indo-Australian Plate and the Sunda Plate is not perpendicular to the plate boundary in this region. Instead, the two plates move at an oblique angle. Most of the convergent strain is accommodated by thrust motion at the plate boundary "megathrust" fault that defines the Sunda Trench. But the oblique motion (the part of the plate motion parallel to the plate boundary) is accommodated by the Great Sumatran Fault, which runs along the volcanic Sunda Arc.
The area between the main plate boundary thrust fault and the Great Sumatran fault forms a "sliver plate" that includes the entire offshore forearc, forearc islands, and the portion of Sumatra west of the Great Sumatran Fault. This sliver plate is not a single rigid bloc, and the details of its internal deformation are under active investigation.[3]
Earthquakes
Listed from northwest to southeast:
- April 2, 1964: Mw 7.0 event near the northern tip of Sumatra and the city Banda Aceh.
- September 19, 1936: Mw 7.2 event (3.685°N 97.535°E)
- March 2007 Sumatra earthquakes: Doublet earthquakes of moment magnitude 6.4 and 6.3 two hours apart northeast of Lake Singkarak.[4]
- 1943 Alahan Panjang earthquakes: Doublet earthquakes of moment magnitude 7.2 and 7.5 occurred within 7 hours of each other on June 8 and 9 southeast of Lake Singkarak.[4]
- 1994 Liwa earthquake: 7.0 Mw event caused 207 deaths near the southern tip of Sumatra.
- June 24, 1933: Mw 7.6 event
See also
References
- Sieh, K.; Natawidjaja, D. (2000), "Neotectonics of the Sumatran fault, Indonesia" (PDF), Journal of Geophysical Research: Solid Earth, Wiley, 105 (B12): 28, 295–28, 326, Bibcode:2000JGR...10528295S, doi:10.1029/2000jb900120
- Fitch, Thomas (1972). "Plate Convergence, Transcurrent Faults, and Internal Deformation Adjacent to Southeast Asia and the Western Pacific". Journal of Geophysical Research. 77 (23): 4432–4460. Bibcode:1972JGR....77.4432F. doi:10.1029/jb077i023p04432. hdl:2060/19720023718.
- Bradley, Kyle (2016). "Implications of the diffuse deformation of the Indian Ocean lithosphere for slip partitioning of oblique plate convergence in Sumatra". Journal of Geophysical Research. 121: 572–591. Bibcode:2017JGRB..122..572B. doi:10.1002/2016JB013549.
- "M 6.4 - southern Sumatra, Indonesia". USGS Earthquake Hazards Program. Retrieved 7 October 2017.