Great Sumatran fault explained

Great Sumatran Fault
Length:	~1650-1900km
Earthquakes:	24 June 1933, 19 Sept 1936, 1943 Alahan Panjang earthquake, 2 April 1964, 1994 Liwa earthquake, March 2007 Sumatra earthquakes
Type:	strike-slip fault
Country:	Indonesia
Other Name:	Semangko Fault
Location:	Sumatra
Plate:	Australian Plate, Eurasian Plate

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. 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.^[1] 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.^[2]

Earthquakes

Listed from northwest to southeast:

• April 2, 1964: M_w 7.0 event near the northern tip of Sumatra and the city Banda Aceh.^[3]
• September 19, 1936: M_w 7.2 event (3.685°N 97.535°E)^[4]
• March 2007 Sumatra earthquakes: Doublet earthquakes of moment magnitude 6.4 and 6.3 two hours apart northeast of Lake Singkarak.^[5]
• 2022 Sumatra earthquake: A magnitude 6.2 earthquake damaged dozens of homes, offices and a school.^{[6] [7]} Six killed and 32 injured.^[8] Felt in Malaysia and Singapore.
• 1926 Padang Panjang earthquakes: Doublet earthquake measuring 6.7 and 6.4. At least 411 people killed.^[9]
• 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.
• 1995 Kerinci earthquake: Moment magnitude 6.8 earthquake, killed at least 84 people and caused 1,868 injuries.^[10]
• 1994 Liwa earthquake: 7.0 M_w event caused 207 deaths near the southern tip of Sumatra.
• 1933 Sumatra earthquake: M_w 7.6 event (5.226°S 104.596°E) southern of Sumatra.^[11] More than 76 people killed and extensive damage. Two towns destroyed.

See also

• Ring of Fire

Further reading

• Rafie . Muhammad Taufiq . Sahara . David P. . Cummins . Phil R. . Triyoso . Wahyu . Widiyantoro . Sri . Stress accumulation and earthquake activity on the Great Sumatran Fault, Indonesia . Natural Hazards . 116 . 3 . 2023 . 0921-030X . 10.1007/s11069-023-05816-2 . 3401–3425. 245719110 .

External links

• Great Sumatran Fault

Notes and References

1. Fitch. Thomas. Plate Convergence, Transcurrent Faults, and Internal Deformation Adjacent to Southeast Asia and the Western Pacific. Journal of Geophysical Research. 77. 23. 4432–4460. 10.1029/jb077i023p04432. 1972JGR....77.4432F. 1972. 2060/19720023718. free.
2. Bradley. Kyle. Implications of the diffuse deformation of the Indian Ocean lithosphere for slip partitioning of oblique plate convergence in Sumatra. Journal of Geophysical Research. 2016. 121. 1 . 10.1002/2016JB013549. 572–591. 2017JGRB..122..572B. free. 10220/42240. free.
3. Web site: M 7.0 - 5 km NE of Banda Aceh, Indonesia. USGS Earthquake Hazards Program. 1 February 2022.
4. Web site: M 7.2 - 90 km WSW of Pangkalan Brandan, Indonesia. USGS Earthquake Hazards Program. 1 February 2022.
5. Web site: M 6.4 - southern Sumatra, Indonesia. USGS Earthquake Hazards Program. 7 October 2017.
6. Web site: M 6.2 - 66 km NNW of Bukittinggi, Indonesia . earthquake.usgs.gov . . 25 February 2022.
7. News: Viola Rahma Hafifah . Nagari Kajai Dilaporkan Terparah Akibat Gempa Pasaman, BPBD Minta Bantuan Medis . 25 February 2022 . Padang Harian Haluan . 25 February 2022 . id.
8. Web site: Gempa di Pasaman dan Pasaman Barat, 6 meninggal termasuk 2 anak-anak, 20 luka-luka - apa yang sejauh ini kita ketahui? . BBC News Indonesia . 2022-02-25 . id . . 2022-02-25.
9. Web site: Jejak Gempa di Aceh dan Sekitarnya. live. 3 December 2021. Tempo.co. 11 April 2012 . https://web.archive.org/web/20190517103431/https://nasional.tempo.co/read/396382/jejak-gempa-di-aceh-dan-sekitarnya . 2019-05-17 .
10. Web site: M 6.8 - 5 km ENE of Sungai Penuh, Indonesia . earthquake.usgs.gov . USGS . 11 August 2021.
11. Web site: M 7.6 - 54 km SW of Kotabumi, Indonesia. USGS Earthquake Hazards Program. 1 February 2022.