2012 Indian Ocean earthquakes
UTC time | 2012-04-11 08:38:36 |
---|---|
2012-04-11 10:43:10 | |
ISC event | 600860404 |
USGS-ANSS | ComCat |
ComCat | |
Local date | 11 April 2012 |
Local time | 15:38 |
17:43 | |
Magnitude | 8.6 Mw[1] |
8.2 Mw | |
Depth | 20.0 km (12.4 mi) |
25.1 km (15.6 mi) | |
Epicenter | 2°18′40″N 93°03′47″E / 2.311°N 93.063°E[2] |
Type | Strike-slip – Intraplate[3] |
Areas affected | Indonesia |
Max. intensity | MMI VII (Very strong) |
Tsunami | Yes |
Foreshocks | 7.2 Mw 10 Jan at 18:36[1] |
Aftershocks | 8.2 Mw 11 April at 10:43[1] |
Casualties | 10 dead[4] 12 injured[4] |
The 2012 Indian Ocean earthquakes were
Tectonic setting
The 2012 earthquake's epicenter was located within the Indo-Australian Plate, which is divided into two sub- or proto-plates: the Indian, and Australian. At their boundary, the Indian and Australian Plates converge at 11 mm (0.4 in) per year in a NNW–SSE direction. This convergence is accommodated by a broad zone of diffuse deformation. As part of that intraplate deformation, north–south trending fracture zones have been reactivated from the Ninety East Ridge as far east as 97°E.[7]
The Indo–Australian Plate was formed after the amalgamation of the Indian Plate and the Australian Plate some 45 million years ago.[8] However, there is a relative movement between the Indian Plate and the Australian Plate. A process which would eventually split the Indo-Australian Plate in two probably started 8 to 10 million years ago and is still taking place. The 2012 Indian Ocean earthquake is associated to the reactivation of the NNE-striking sea floor fabric.[9][10]
Earthquake
The magnitude 8.6 (Mw) earthquake occurred about 610 km (379 mi) southwest of Banda Aceh, Indonesia at 08:38 UTC on 11 April 2012. The earthquake occurred at a depth of 22.9 km (14.2 mi), which is considered relatively shallow according to the scale used by the United States Geological Survey (USGS).[2] The quake was originally reported as a magnitude 8.9, but was later downgraded to 8.6. It was felt as far away as Malaysia, the Maldives and in India.[11] The earthquake was caused by a strike-slip motion. The earthquake and the largest aftershock had a fault displacement of 21.3 m (70 ft).[12] The strike-slip nature of the earthquake meant that the movement displaced relatively little seawater and was less likely to cause a tsunami.[13]
Both the initial earthquake and the magnitude 8.2 aftershock were classified (based on their
These earthquakes have a complex rupture process. The rupture of these earthquakes occurred on multiple, almost orthogonal faults. This is rare in a single earthquake. This earthquake had an overall relatively slow rupture speed, although the speed was
Damage
Four people in their 60s and 70s in Banda Aceh, and a 39-year-old man in Lhokseumawe died from heart attacks or shock. Injuries were reported in Aceh Singkil, including a child who was critically injured by a falling tree.[19] The quake prompted people in Indonesia, Thailand and India to leave their homes and offices in fear of tsunamis.[20] People headed for higher ground in parts of Indonesia and Malaysia.[11][21] In Aceh, where 31,000 people were killed in the 2004 Indian Ocean earthquake and tsunami, people were reported weeping.[22] Some people used cars and motorcycles to reach higher ground. Patients were reportedly wheeled out of hospitals, some with drips attached to their arms. One hotel guest was slightly injured when he jumped out of his window to save himself.[23]
The earthquake was felt over a large area, including Indonesia, the Maldives, Sri Lanka, India, Nepal, Bhutan, China, Bangladesh, Myanmar, Thailand, Malaysia, Laos, Cambodia, Singapore, and Vietnam.
Aftershocks
A magnitude 8.2 aftershock struck at a depth of 16.4 kilometres (10.2 mi) about 430 km (267 mi) southwest of Banda Aceh at 10:43 UTC, two hours after the initial earthquake.[31] It was oddly reported as an 8.8 Mw before being quickly downgraded.[32] Many aftershocks with magnitude readings between 5.0 and 6.0 were recorded for several hours after the initial earthquake which hit the west coast of northern Sumatra.[33][34] Since the initial magnitude 8.6 earthquake, there have been 111 aftershocks over magnitude 4.0 according to USGS, including a magnitude 6.2 on 15 April 2012.[35][36]
Tsunami warnings
Three hours after the initial quake it was still unclear whether a tsunami had been generated or if a tsunami had done any significant damage. A geophysicist from the Pacific Tsunami Warning Center (PTWC) stated that a gauge closest to the epicenter recorded a wave peak of about 1 m (3 ft).[37] The Pacific Tsunami Warning Center said that at 10:14 UTC that a tsunami was generated and may have already caused some coastal destruction.[38] A seismologist from the British Geological Survey[39] said that the "tearing earthquake" displaced relatively little water and was therefore unlikely to cause a significant tsunami.[24] Indonesian authorities also issued a statement saying that the likelihood of a tsunami was low.[40]
Tsunami warnings were issued in the following countries:
India
After the earthquake, the Indian National Centre for Ocean Information Services (INCOIS) issued a high-level tsunami warning for the Andaman and Nicobar Islands.[41] Authorities told civilians to move away from the coast and towards higher ground.[42] Areas subject to warnings included
In Kolkata, underground Metro Railways services were stopped and tall office buildings and shopping malls were evacuated. Navy warships were put on high alert. The Indian Air Force dispatched two C-130s and one Il-76 aircraft to the Andaman islands.[44]
Sri Lanka
The Ministry of Disaster Management and Human Rights (Sri Lanka) authorised an evacuation order[45] at 9:08 UTC advising people living near coastal regions to move to higher ground. The initial quake was not expected to affect Sri Lanka, but aftershocks were being monitored.[46] Deputy Director M. D. Dayananda said that a tsunami could hit Trincomalee.[11]
As part of a
Thailand
Six Andaman coast provinces urged people to go to high ground and stay away from areas that could be affected. Phuket International Airport was closed.[11] The alerts caused panic as people fled buildings and made for high ground.[citation needed]
During the initial earthquake and for more than two hours after, none of Thailand's free television stations reported the earthquake or tsunami warnings, preferring to continue a live broadcast of a
Tsunami
Small 0.5 m (20 in) waves, within regular tide limits, were reported in the Campbell Bay area of
See also
References
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- ^ a b "Magnitude 8.6 – OFF THE WEST COAST OF NORTHERN SUMATRA". United States Geological Survey. 11 April 2012. Archived from the original on 6 September 2017. Retrieved 11 April 2012.
- ^ a b Prasad, R. (12 April 2012). "Why April 11 quake was caused by a strike-slip fault". The Hindu. Chennai, India. Retrieved 13 April 2012.
- ^ a b USGS. "M8.6 – off the west coast of northern Sumatra". United States Geological Survey.
- ^ NewsCore (11 April 2012). "Indian Ocean tsunami alert cancelled after two strong quakes hit off Sumatra, Indonesia". Herald Sun. Retrieved 11 April 2012.
- ^ "Huge quake strikes off Indonesia, tsunami warning issued". Reuters. 11 April 2012. Retrieved 11 April 2012.
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- ^ "The 2012 Mw 8.6 Sumatra earthquake: Evidence of westward sequential seismic ruptures associated to the reactivation of a N–S ocean fabric" by C. Satriano, E. Kiraly, P. Bernard, and J.-P. Vilotte
- ^ a b c d e f g "Indian Ocean on tsunami alert after quakes". Al Jazeera. 11 April 2012. Retrieved 11 April 2012.
- ^ "Scientists: Magnitude-8.6 Indonesia jolt was unusually large for a strike-slip quake; Winnipeg Free Press". The Canadian Press. 11 April 2012. Retrieved 11 April 2012.
- ^ "Explained: What is a slip-strike quake, and why there was no tsunami – World – DNA". Daily News and Analysis. 11 April 2012.
- ^ United States Geological Survey (11 April 2012). "Poster of the M8.6 Northern Sumatra, Earthquake of 11 April 2012" (PDF). Retrieved 12 April 2012.
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- ^ S2CID 130085680. Archived from the original(PDF) on 4 March 2016. Retrieved 1 January 2015.
- ^ "Séismes au large de Sumatra mercredi 11 avril 2012" (in French). Institut de Physique du Globe de Paris. Archived from the original on 24 June 2013. Retrieved 9 February 2013.
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- ^ "Massive earthquake strikes Indonesia, tremors felt in India". The Times of India. Reuters. 11 April 2012. Retrieved 11 April 2012.
- ^ "Massive earthquake off Indonesia". TVNZ. 11 April 2012. Retrieved 11 April 2012.
- ^ NDTV News. "Strong Indonesian quakes cause panic, not tsunami". Associated Press. Retrieved 12 April 2012.
Women and children cried in Aceh, where memories of a 2004 tsunami that killed 170,000 people in that province alone are still raw. Others screamed "God is great" as they poured from their homes or searched frantically for separated family members
- ^ NDTV News. "Strong Indonesian quakes cause panic, not tsunami". Associated Press. Retrieved 12 April 2012.
- ^ a b "Indian Ocean tsunami alert lifted after Aceh quake". BBC News. 11 April 2012. Retrieved 11 April 2012.
- ^ "Strong earthquake in Sumatra slightly felt in Yangon – Xinhua | English.news.cn". Xinhua News Agency. Archived from the original on 23 August 2014. Retrieved 12 April 2012.
- ^ The Brief » Blog Archive » Tremors felt. Nepali Times. Retrieved 13 April 2012.
- ^ "News : Tremors across eastern coast; people evacuated from Andamans". The Hindu. Chennai, India. Press Trust of India. 11 April 2012. Retrieved 11 April 2012.
- ^ "8.6 earthquake hits Aceh, tsunami alert issued (Update) | theSundaily". The Sun. Malaysia. 11 April 2012. Retrieved 11 April 2012.[permanent dead link]
- ^ "Large Aceh quake triggers Indian Ocean tsunami warning – Tremor felt in Colombo | Independent Television Network News". Itnnews.lk. 11 April 2012. Retrieved 11 April 2012.
- ^ 专家表示:印尼地震造成我国西藏地区有震感属正常 – 新华社会 – 新华网. News.xinhuanet.com. Retrieved 13 April 2012.
- ^ "8.2-magnitude aftershock hits off Sumatra". US Geological Survey (USGS). 11 April 2012. Archived from the original on 13 April 2012. Retrieved 11 April 2012.
- ^ "New tsunami warning after magnitude 8.8 aftershock in Indonesia". ITV News. 11 April 2012. Retrieved 26 July 2021.
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- ^ "Earthquake in Indonesia: India withdraws tsunami warning". NDTV. 11 April 2012. Retrieved 11 April 2012.
- ^ TOI, Times of India (12 April 2012). "8.6 magnitude quake in Aceh triggers tsunami fears in India". The Times of India. Archived from the original on 30 July 2013.
- ^ "Tsunami warning in South and East | Top Story". Daily Mirror. 11 April 2012. Archived from the original on 14 April 2012. Retrieved 11 April 2012.
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- ^ "Trains stopped, power to be disconnected | Breaking News". Daily Mirror. 11 April 2012. Archived from the original on 14 April 2012. Retrieved 11 April 2012.
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- ^ "สุภิญญา"ชี้แจง "กสทช."ร่อนจดหมายด่วนฟรีทีวีทุกช่อง "นำเสนอข่าวแผ่นดินไหว-สึนามิ" [Suphinya shows up the NBTC letter ordering every free television channel to present earthquake-tsunami news] (in Thai). Matichon. 11 April 2012. Archived from the original on 7 July 2014.
- ^ ThaiPBS. 12 April 2012.
- The Daily Star. 11 April 2012. Archived from the originalon 25 May 2012. Retrieved 11 April 2012.
- ^ "Strong Indonesian quakes cause panic across Asia, not tsunami". Emirates 24/7. 11 April 2012. Retrieved 11 April 2012.
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- Sources
- Pollitz, F.F.; Bürgmann, R.;
Further reading
- Dixit, M.; Ram Bansal, A.; Mangalalampally, R. K.; Singha Roy, K.; Teotia, S. S. (2022), "Dynamically Triggered Events in a Low Seismically Active Region of Gujarat, Northwest India, during the 2012 Mw 8.6 Indian Ocean Earthquake", Bulletin of the Seismological Society of America, 112 (4): 1908–1920, S2CID 248768288
- Kumar, T. S.; Nayak, S.; Kumar, Ch. P.; Yadav, R. B. S.; Kumar, B. A.; Sunanda, M. V.; Devi, E. U.; Kumar, N. K.; Kishore, S. A.; Shenoi, S. S. C. (2012), "Successful monitoring of the 11 April 2012 tsunami off the coast of Sumatra by Indian Tsunami Early Warning Centre", Current Science, 102 (11): 1519–1526, JSTOR 24084760
- Laiyin Guo, Jian Lin, Hongfeng Yang, Jinyu Tian; Aftershocks of the 2012 Mw 8.6 Wharton Basin Intraplate Earthquake in the Eastern Indian Ocean Revealed by Near‐Field Ocean‐Bottom Seismometers. Seismological Research Letters 2021; doi: https://doi.org/10.1785/0220210096
External links
- Media related to 2012 Indian Ocean earthquake at Wikimedia Commons
- Satellite View at Wikimapia.org
- Preliminary source parameters obtained by automatic analysis – 2012/04/11 08:38 Off West Coast of Northern Sumatra – International seismic network, NIED, Japan
- After major earthquake, silence: Dynamic stressing of a global system of faults results in rare seismic silence – Science Daily
- Rare great earthquake in April triggers large aftershocks all over the globe – Science Daily
- The International Seismological Centre has a bibliography and/or authoritative data for this event.