2012 Indian Ocean earthquakes

{{see also|Strike-slip tectonics|Wharton Basin}}

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 {{convert|11|mm|in|1|abbr=on}} 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.{{cite journal|last=Kreemer|first=C.|author2=Holt W.E. & Haines A.J.|year=2003|title=An integrated global model of present-day plate motions and plate boundary deformation|journal=Geophysical Journal International|volume=154|issue=1|pages=8–34|bibcode=2003GeoJI.154....8K|doi=10.1046/j.1365-246X.2003.01917.x|last3=Haines|first3=A. John|doi-access=free}}

The Indo–Australian plate was formed after the amalgamation of the Indian plate and the Australian plate some 45 million years ago.{{citation|title=Ridge torques and continental collision in the Indian-Australian plate|url=http://jaeger.earthsci.unimelb.edu.au/msandifo/Publications/Manuscripts/Manuscripts/1995_Geology.pdf|first1=M.|last1=Sanford|first2=D.D.|last2=Coblentz|first3=R.M.|last3=Richardson|year=1995|journal=Geology|volume=23|number=7|pages=653–656|bibcode=1995Geo....23..653S|doi=10.1130/0091-7613(1995)023<0653:RTACCI>2.3.CO;2|access-date=24 February 2013|archive-date=20 April 2013|archive-url=https://web.archive.org/web/20130420111351/http://jaeger.earthsci.unimelb.edu.au/msandifo/Publications/Manuscripts/Manuscripts/1995_Geology.pdf|url-status=dead}} 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.{{cite news|url=https://www.bbc.co.uk/news/science-environment-19732681|publisher=BBC News|title=April Sumatra quakes signal Indian ocean plate break-up|date=26 September 2012}}"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

The magnitude 8.6 (M_w) earthquake occurred about {{convert|610|km|mi|0|abbr=on}} southwest of Banda Aceh, Indonesia at 08:38 UTC on 11 April 2012. The earthquake occurred at a depth of {{convert|22.9|km|mi|1|abbr=on}}, which is considered relatively shallow according to the scale used by the United States Geological Survey (USGS).{{cite web|url=https://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc000905e.php#details|title=Magnitude 8.6 – OFF THE WEST COAST OF NORTHERN SUMATRA|publisher=United States Geological Survey|access-date=11 April 2012|date=11 April 2012|archive-url=https://web.archive.org/web/20170906210236/https://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc000905e.php#details|archive-date=6 September 2017|url-status=dead}} 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. The earthquake was caused by a strike-slip motion. The earthquake and the largest aftershock (magnitude 8.2, at 10:43 UTC on 11 April) had a fault displacement of {{convert|21.3|m|ft|0|abbr=on}}.{{cite news|url=http://www.winnipegfreepress.com/arts-and-life/life/sci_tech/scientists-magnitude-86-indonesia-jolt-was-unusually-large-for-a-strike-slip-quake-147075955.html|title=Scientists: Magnitude-8.6 Indonesia jolt was unusually large for a strike-slip quake; Winnipeg Free Press|agency=The Canadian Press|date=11 April 2012|access-date=11 April 2012}} The strike-slip nature of the earthquake meant that the movement displaced relatively little seawater and was less likely to cause a tsunami.{{cite web|url=http://www.dnaindia.com/world/report_explained-what-is-a-slip-strike-quake-and-why-there-was-no-tsunami_1674556|title=Explained: What is a slip-strike quake, and why there was no tsunami – World – DNA|work=Daily News and Analysis|date=11 April 2012}}

File:USGS map of the 2012 Indian Ocean Earthquake.jpg ShakeMap for the M8.6 event]]

Both the initial earthquake and the magnitude 8.2 aftershock were classified (based on their focal mechanisms) as strike-slip earthquakes, meaning that the crust on either side shifted against each other horizontally, rather than vertically. Since 2006 there have been three other earthquakes in the area with a similar faulting style. All these earthquakes were consistent with either left-lateral slip on SSW–NNE orientated strike-slip faults, or right-lateral slip on WNW–ESE orientated strike-slip faults, both compatible with the direction of convergence.{{cite web|url=ftp://hazards.cr.usgs.gov/maps/sigeqs/20120411/20120411.pdf|title=Poster of the M8.6 Northern Sumatra, Earthquake of 11 April 2012|publisher=United States Geological Survey|date=11 April 2012|archive-url=https://web.archive.org/web/20220121035946/ftp://hazards.cr.usgs.gov/maps/sigeqs/20120411/20120411.pdf|archive-date=2022-01-21|url-status=dead|access-date=12 April 2012}} A back projection analysis of data collected by Hi-net, an observation network in Japan, found a complex pattern of four conjugate faults. There was a strong correlation between the fault rupture pattern and the distribution of the aftershocks.{{cite journal|url=http://www.eqh.dpri.kyoto-u.ac.jp/~mori/backprojection/sumatra.html|title=Supershear rupture on multiple faults for the Mw 8.6 Off Northern Sumatra, Indonesia earthquake of April 11, 2012|first1=D.|last1=Wang|first2=J.|last2=Mori|first3=T.|last3=Uchide|journal=Geophysical Research Letters|year=2012|volume=39|issue=21|pages=n/a|doi=10.1029/2012GL053622|bibcode=2012GeoRL..3921307W|doi-access=free}}

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 above the S-wave velocity in some fault segments. The rupture may have affected the crust and the upper mantle according to the kinematic source inversion.{{cite web|url=http://www.ipgp.fr/pages/040119.php?langue=0|title=Séismes au large de Sumatra mercredi 11 avril 2012|publisher=Institut de Physique du Globe de Paris|access-date=9 February 2013|language=fr|archive-url=https://web.archive.org/web/20130624151105/http://www.ipgp.fr/pages/040119.php?langue=0|archive-date=24 June 2013|url-status=dead}} The rupture was caused by ductile shear heating instability which is different from frictional failure and operates between {{convert|600|-|800|C}}, which corresponds to about the depths of {{convert|40-60|km|abbr=on}}. The serpentinization of oceanic lithosphere can lead to a low friction coefficient, but the reaction is possible only up to {{convert|400|-|500|C}}, which corresponds to the depth of about {{convert|25|km|abbr=on}}. A single dynamic weakening mechanism which can work over the whole range of slip of this earthquake is still to be identified.{{cite journal|url=http://web.gps.caltech.edu/~tsai/files/Meng_etal_Science2012All.pdf|title=Earthquake in a Maze: Compressional Rupture Branching During the 2012 Mw 8.6 Sumatra Earthquake|first1=L.|last1=Meng L.|first2=J.-P.|last2=Ampuero|first3=J.|last3=Stock|first4=Z.|last4=Duputel|first5=Y.|last5=Luo|first6=V.C.|last6=Tsai|year=2012|journal=Science|volume=337|number=6095|pages=724–726|doi=10.1126/science.1224030|pmid=22821986|bibcode=2012Sci...337..724M|s2cid=130085680|access-date=1 January 2015|archive-date=4 March 2016|archive-url=https://web.archive.org/web/20160304050553/http://web.gps.caltech.edu/~tsai/files/Meng_etal_Science2012All.pdf|url-status=dead}}{{cite journal|url=http://211.144.68.84:9998/91keshi/Public/File/41/336-6085/pdf/1118.full.pdf|title=A Rogue Earthquake Off Sumatra|first1=J.|last1=McGuire|first2=G.C.|last2=Beroza|author-link2=Gregory Beroza|journal=Science|year=2012|volume=336|issue=6085|pages=1118–1119|doi=10.1126/science.1223983|bibcode=2012Sci...336.1118M|pmid=22582017|s2cid=206542279|access-date=13 August 2012|archive-url=https://web.archive.org/web/20131029211452/http://211.144.68.84:9998/91keshi/Public/File/41/336-6085/pdf/1118.full.pdf|archive-date=29 October 2013|url-status=dead}}

Ten people died from heart attacks or shock; six from Aceh Besar Regency, and one each from Banda Aceh, Lhokseumawe, Aceh Barat Daya and Padang Pariaman. Four serious injuries and eight minor injuries were reported in Aceh Singkil, Aceh Barat, Aceh Selatan and Simeulue regencies including a child who was critically injured by a falling tree.Jakarta BNPB{{cite news|url=https://news.detik.com/berita/d-1892236/korban-meninggal-gempa-dan-tsunami-aceh-jadi-10-orang/2|title=Korban Meninggal Gempa dan Tsunami Aceh Jadi 10 Orang|work=Detik.com|date=12 April 2012|access-date=15 September 2024}} People in Indonesia, Thailand and India left their homes and offices in fear of tsunamis.{{cite news|agency=Reuters|url=http://timesofindia.indiatimes.com/india/Massive-earthquake-strikes-Indonesia-tremors-felt-in-India/articleshow/12622534.cms|title=Massive earthquake strikes Indonesia, tremors felt in India|newspaper=The Times of India|date=11 April 2012|access-date=11 April 2012}} People headed for higher ground in parts of Indonesia and Malaysia.{{cite web|url=http://tvnz.co.nz/world-news/massive-earthquake-off-indonesia-4828379|access-date=11 April 2012|date=11 April 2012|publisher=TVNZ|title=Massive earthquake off Indonesia}} In Aceh, where 31,000 people were killed in the 2004 Indian Ocean earthquake and tsunami, people were reported weeping.{{cite news|author=NDTV News|title=Strong Indonesian quakes cause panic, not tsunami|url=http://www.ndtv.com/article/world/strong-indonesian-quakes-cause-panic-not-tsunami-196545?pfrom=home-world|agency=Associated Press|access-date=12 April 2012|quote=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}} 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.{{cite news|author=NDTV News|title=Strong Indonesian quakes cause panic, not tsunami|url=http://www.ndtv.com/article/world/strong-indonesian-quakes-cause-panic-not-tsunami-196545?pfrom=home-world|agency=Associated Press|access-date=12 April 2012}} In Aceh Barat, one bridge collapsed and a dormitory was damaged. One home and the walls of a prison collapsed, and another house and an office was damaged in Aceh Besar.

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.{{cite news|url=https://www.bbc.co.uk/news/world-asia-17675399|title=Indian Ocean tsunami alert lifted after Aceh quake|publisher=BBC News|date=11 April 2012|access-date=11 April 2012}}{{cite web|url=http://news.xinhuanet.com/english/world/2012-04/11/c_131520443.htm|archive-url=https://web.archive.org/web/20140823115212/http://news.xinhuanet.com/english/world/2012-04/11/c_131520443.htm|url-status=dead|archive-date=23 August 2014|title=Strong earthquake in Sumatra slightly felt in Yangon – Xinhua {{pipe}} English.news.cn|agency=Xinhua News Agency|access-date=12 April 2012}}[http://www.nepalitimes.com/blogs/thebrief/2012/04/11/tremors-felt-2/ The Brief » Blog Archive » Tremors felt]. Nepali Times. Retrieved 13 April 2012. Shaking was felt across the eastern coast of India including Chennai, Bangalore, Kochi, Bhubaneswar, Vizag and Kolkata. The Metro Rail services were suspended in Kolkata, and passengers were asked to leave stations.{{cite news|agency=Press Trust of India|url=http://www.thehindu.com/news/article3303405.ece|title=News : Tremors across eastern coast; people evacuated from Andamans|work=The Hindu|date=11 April 2012|access-date=11 April 2012|location=Chennai, India}} In peninsular Malaysia, shaking was felt in Penang and Kuala Lumpur.{{cite web|url=http://www.thesundaily.my/news/346788|title=8.6 earthquake hits Aceh, tsunami alert issued (Update) {{pipe}} theSundaily|work=The Sun|location=Malaysia|date=11 April 2012|access-date=11 April 2012}}{{Dead link|date=September 2018 |bot=InternetArchiveBot |fix-attempted=yes }} The tremor was felt in Colombo, Sri Lanka, where people in some high-rise buildings were evacuated.{{cite web|url=http://www.itnnews.lk/latest/?p=38153|title=Large Aceh quake triggers Indian Ocean tsunami warning – Tremor felt in Colombo {{pipe}} Independent Television Network News|work=Itnnews.lk|date=11 April 2012|access-date=11 April 2012}} In China, the earthquake was felt in Tibet, however, while places closer to the epicenter such as Yunnan and Guangxi did not report shaking.[https://web.archive.org/web/20140823115307/http://news.xinhuanet.com/society/2012-04/12/c_111772595.htm 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.

A magnitude 8.2 aftershock struck at a depth of {{convert|16.4|km|mi}} about {{convert|430|km|mi|0|abbr=on}} southwest of Banda Aceh at 10:43 UTC, two hours after the initial earthquake.{{cite news|title=8.2-magnitude aftershock hits off Sumatra|url=https://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc00090da.php|publisher=United States Geological Survey (USGS)|date=11 April 2012|access-date=11 April 2012|archive-url=https://web.archive.org/web/20120413234018/http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc00090da.php|archive-date=13 April 2012|url-status=dead}} It was oddly reported as an 8.8 {{M|w|link=y}} before being quickly downgraded.{{Cite web|title=New tsunami warning after magnitude 8.8 aftershock in Indonesia|url=https://www.itv.com/news/update/2012-04-11/new-tsunami-warning-after-magnitude-8-8-aftershock-in-indonesia/|publisher=ITV News|date=11 April 2012|access-date=26 July 2021}} 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.{{cite web|url=https://earthquake.usgs.gov/earthquakes/eventpage/usc00090da|title=M8.2 – off the west coast of northern Sumatra|publisher=United States Geological Survey|access-date=11 April 2012|date=11 April 2012}}{{cite web|url=https://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/quakes_big.php|title=Latest Earthquakes M5.0+ in the World – Past 7 days|publisher=United States Geological Survey|date=11 April 2012|access-date=11 April 2012|url-status=dead|archive-url=https://web.archive.org/web/20101124010921/http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/quakes_big.php|archive-date=24 November 2010}} 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.{{cite web|url=https://earthquake.usgs.gov/earthquakes/recenteqsww/Maps/10/90_0.php|title=10-degree Map Centered at 0°N,90°E|date=16 April 2012|publisher=United States Geological Survey|access-date=16 April 2012|archive-url=https://web.archive.org/web/20130408063916/http://earthquake.usgs.gov/earthquakes/recenteqsww/Maps/10/90_0.php|archive-date=8 April 2013|url-status=dead}}{{cite web|url=https://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc000941x.php|title=Magnitude 6.2 – off the West Coast of Northern Sumatra|date=15 April 2012|publisher=United States Geological Survey|access-date=16 April 2012|url-status=dead|archive-url=https://web.archive.org/web/20120418063825/http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc000941x.php|archive-date=18 April 2012}}

File:Earthquake Leads Office Evacuation - Sector-V - Salt Lake City - Kolkata 2012-04-11 9367.JPG, India, in front of the Cognizant building.]]

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 {{convert|1|m|ft|0|abbr=on}}.{{Cite news|url=http://www.indianexpress.com/news/indonesia-earthquake-no-damage-to-ocean-basin-india-withdraws-tsunami-warning/935470|title=Indonesia earthquake: No damage to ocean basin, India withdraws tsunami warning|newspaper=The Indian Express|date=11 April 2012|access-date=11 April 2012}} The Pacific Tsunami Warning Center said that at 10:14 UTC that a tsunami was generated and may have already caused some coastal destruction.{{cite web|url=http://ptwc.weather.gov/ptwc/text.php?id=indian.TSUIOX.2012.04.11.1014|title=Pacific Tsunami Warning Center/NOAA/NWS: Tsunami bulletin number 003|publisher=PTWC|access-date=11 April 2012|date=11 April 2012|archive-url=https://web.archive.org/web/20120413231854/http://ptwc.weather.gov/ptwc/text.php?id=indian.TSUIOX.2012.04.11.1014|archive-date=13 April 2012|url-status=dead}} A seismologist from the British Geological Survey{{cite web|url=http://www.bgs.ac.uk/staff/profiles/1331.html|title=Staff Profile of Dr Roger Musson {{pipe}} British Geological Survey|publisher=BGS|access-date=12 April 2012}} said that the "tearing earthquake" displaced relatively little water and was therefore unlikely to cause a significant tsunami. Indonesian authorities also issued a statement saying that the likelihood of a tsunami was low.{{cite news|url=https://newsfeed.time.com/2012/04/11/watch-indonesia-reacts-to-8-7-magnitude-earthquake/|title=Watch: Indonesia Reacts to 8.7 Magnitude Earthquake|work=TIMES|date=11 April 2012|access-date=11 April 2012}}

Tsunami warnings were issued in the following countries: Indonesia, Australia, Cambodia, Malaysia, Singapore, Thailand, Myanmar, Bangladesh, India, Sri Lanka, Maldives, Pakistan, Iran, United Arab Emirates, Oman, Yemen, Somalia, Kenya, Tanzania, Seychelles, Mozambique, Mauritius, Comoros, Madagascar, South Africa and the dependencies of Diego Garcia as part of the British Indian Ocean Territories, Crozet Islands, Réunion and Kerguelen Islands. Projected tsunami arrival times in GMT were: 8:38 for Indonesia, 11:38 for Sri Lanka, 14:38 for the Seychelles, 17:38 for Madagascar and 20:38 for South Africa.{{cite news|title=Indian Ocean on tsunami alert after quakes|url=http://www.aljazeera.com/news/asia-pacific/2012/04/201241185126462944.html|publisher=Al Jazeera|date=11 April 2012|access-date=11 April 2012}}

After the earthquake, the Indian National Centre for Ocean Information Services (INCOIS) issued a high-level tsunami warning for the Andaman and Nicobar Islands.{{cite news|agency=Agence France-Presse|url=http://timesofindia.indiatimes.com/india/Indonesia-quake-India-issues-tsunami-warning-for-Andaman-and-Nicobars/articleshow/12622459.cms|title=Indonesia earthquake: India issues tsunami warning for Andaman and Nicobars|newspaper=The Times of India|date=11 April 2012|access-date=11 April 2012}} Authorities told civilians to move away from the coast and towards higher ground.{{cite web|url=http://www.ndtv.com/article/india/earthquake-in-indonesia-how-india-responded-196432|title=Earthquake in Indonesia: How India responded|publisher=NDTV|date=11 April 2012|access-date=11 April 2012}}

Areas subject to warnings included Tamil Nadu, Andhra Pradesh and the Union Territory of Andaman and Nicobar Islands.{{cite web|url=http://www.ndtv.com/article/india/earthquake-in-indonesia-india-withdraws-tsunami-warning-196421|title=Earthquake in Indonesia: India withdraws tsunami warning|publisher=NDTV|date=11 April 2012|access-date=11 April 2012}} Prabkhakar Rao of the disaster control room in Port Blair said that there could be tsunamis as high as {{convert|1.5|m|ft|1|abbr=on}} at Port Blair and {{convert|3.9|m|ft|1|abbr=on}} at Campbell Bay.

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.{{cite news|work=The Times of India|title=8.6 magnitude quake in Aceh triggers tsunami fears in India|url=http://articles.timesofindia.indiatimes.com/2012-04-12/india/31330570_1_tsunami-warning-indonesian-coast-massive-earthquake|archive-url=https://web.archive.org/web/20130730154630/http://articles.timesofindia.indiatimes.com/2012-04-12/india/31330570_1_tsunami-warning-indonesian-coast-massive-earthquake|url-status=dead|archive-date=30 July 2013|date=12 April 2012}}

File:Sri lanka DMC evacuation order issued 11 April.jpg]]

The Ministry of Disaster Management and Human Rights (Sri Lanka) authorised an evacuation order{{cite web|url=http://dailymirror.lk/top-story/17902-tsunami-warning-in-south-and-east.html|title=Tsunami warning in South and East {{pipe}} Top Story|work=Daily Mirror|date=11 April 2012|access-date=11 April 2012|archive-url=https://web.archive.org/web/20120414025955/http://www.dailymirror.lk/top-story/17902-tsunami-warning-in-south-and-east.html|archive-date=14 April 2012|url-status=dead}} 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.{{cite web|url=http://www.meteo.gov.lk/index.php?option=com_content&view=article&id=63&Itemid=72&lang=en|title=Tsunami Warning Evacuation Bulletin|date=11 April 2012|access-date=11 April 2012}} Deputy Director M. D. Dayananda said that a tsunami could hit Trincomalee.

As part of a risk mitigation measure, the Ceylon Electricity Board disconnected power supplies to coastal areas and railway control rooms. Coastal train services were suspended.{{cite web|url=http://www.dailymirror.lk/news/17904-trains-stopped-power-to-be-disconnected.html|title=Trains stopped, power to be disconnected {{pipe}} Breaking News|work=Daily Mirror|date=11 April 2012|access-date=11 April 2012|archive-url=https://web.archive.org/web/20120414034054/http://www.dailymirror.lk/news/17904-trains-stopped-power-to-be-disconnected.html|archive-date=14 April 2012|url-status=dead}} The Road Development Authority removed toll charges from the Southern Sri Lanka Distributor to aid the evacuation.{{cite web|url=http://www.dailymirror.lk/news/17905-expressway-free-of-charge.html|title=Expressway free of charge {{pipe}} Breaking News|work=Daily Mirror|date=11 April 2012|access-date=11 April 2012|archive-url=https://web.archive.org/web/20120414034059/http://www.dailymirror.lk/news/17905-expressway-free-of-charge.html|archive-date=14 April 2012|url-status=dead}} Coastal bus services were temporarily re-routed.{{cite web|url=http://www.dailymirror.lk/news/17906-private-buses-stop-in-coastal-areas.html|title=Private buses stop in coastal areas {{pipe}} Breaking News|work=Daily Mirror|date=11 April 2012|access-date=11 April 2012|archive-url=https://web.archive.org/web/20120414041825/http://www.dailymirror.lk/news/17906-private-buses-stop-in-coastal-areas.html|archive-date=14 April 2012|url-status=dead}}

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. The alerts caused panic as people fled buildings and made for high ground.{{Citation needed|date=April 2012}}

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 royal family ceremony, despite the National Broadcasting and Telecommunications Commission (NBTC)'s urgent order directing the emergency information to be broadcast instead without delay.{{cite web|url=http://www.matichon.co.th/news_detail.php?newsid=1334151031|script-title=th:"สุภิญญา"ชี้แจง "กสทช."ร่อนจดหมายด่วนฟรีทีวีทุกช่อง "นำเสนอข่าวแผ่นดินไหว-สึนามิ"|trans-title=Suphinya shows up the NBTC letter ordering every free television channel to present earthquake-tsunami news|language=th|date=11 April 2012|publisher=Matichon|url-status=dead|archive-url=https://web.archive.org/web/20140707045541/http://www.matichon.co.th/news_detail.php?newsid=1334151031|archive-date=7 July 2014}} This caused criticism on the internet, although it was muted by a lèse majesté law.{{cite web|url=https://www.youtube.com/watch?v=xddZ6zbx2dY|script-title=th:"ทีวีพูล"แผ่นดินไหวช่วงพระราชพิธี|trans-title=TV Pools, Earthquake and Royal Ceremony|language=th|date=12 April 2012|publisher=ThaiPBS}} The Television Pool of Thailand defended their actions, saying that running texts about the warnings were displayed onscreen during the broadcast.

Small {{convert|0.5|m|in|0|abbr=on}} waves, within regular tide limits, were reported in the Campbell Bay area of Great Nicobar Island, and {{convert|10|cm|in|0|abbr=on}} waves were reported in Thailand.{{cite journal|title=Small tsunami reaches Thailand after huge quake|url=http://www.dailystar.com.lb/News/International/2012/Apr-11/169905-small-tsunami-reaches-thailand-after-huge-quake.ashx|date=11 April 2012|journal=The Daily Star|access-date=11 April 2012|archive-date=25 May 2012|archive-url=https://web.archive.org/web/20120525021037/http://www.dailystar.com.lb/News/International/2012/Apr-11/169905-small-tsunami-reaches-thailand-after-huge-quake.ashx|url-status=dead}}{{cite web|title=Strong Indonesian quakes cause panic across Asia, not tsunami|url=http://www.emirates247.com/news/world/strong-indonesian-quakes-cause-panic-across-asia-not-tsunami-2012-04-11-1.453403|date=11 April 2012|publisher=Emirates 24/7|access-date=11 April 2012}} The Indonesian Agency for Meteorology, Climatology and Geophysics said three small tsunamis struck the Aceh coast. The highest was {{convert|80|cm|in|0|abbr=on}}, at Meulaboh.{{cite web|url=http://www.thejakartaglobe.com/news/update-indonesia-lifts-tsunami-warning-residents-return-home/510788|title=Update: Indonesia Lifts Tsunami Warning, Residents Return Home|work=Jakarta Globe|date=11 April 2012|access-date=11 April 2012|url-status=dead|archive-url=https://web.archive.org/web/20120415041414/http://www.thejakartaglobe.com/news/update-indonesia-lifts-tsunami-warning-residents-return-home/510788|archive-date=15 April 2012}} After the sea was seen receding about {{convert|10|m}} at Simeulue, a {{convert|1|m|ft|0|abbr=on}} wave was observed. Simeulue is an island of fishing villages {{convert|150|km|abbr=on}} off the west coast of Sumatra.{{cite web|url=http://au.news.yahoo.com/world/a/-/world/13397953/indonesian-quake-reawakens-tsunami-fears-in-asia|title=Terrified Indonesian island survives quake – Yahoo!7|publisher=Yahoo News|access-date=12 April 2012|url-status=dead|archive-url=https://web.archive.org/web/20120413144123/http://au.news.yahoo.com/world/a/-/world/13397953/indonesian-quake-reawakens-tsunami-fears-in-asia|archive-date=13 April 2012}}

• List of earthquakes in 2012
• List of earthquakes in Indonesia

{{Reflist|refs=

{{cite web|title=M8.6 – off the west coast of northern Sumatra|url=https://earthquake.usgs.gov/earthquakes/eventpage/usp000jhh2#general_region|publisher=United States Geological Survey}}

{{citation|title=Modeling the 2012 Wharton Basin earthquakes off-Sumatra: Complete Lithospheric failure|url=http://web.gps.caltech.edu/~avouac/publications/Wei_JGR2013.pdf|first1=S.|last1=Wei|first2=D.|last2=Helberger|first3=J-P.|last3=Avounac|year=2013|journal=Journal of Geophysical Research|volume=118|issue=7|pages=3595|doi=10.1002/jgrb.50267|bibcode=2013JGRB..118.3592W|doi-access=free}}

}}

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• {{citation|last1=Dixit|first1=M.|last2=Ram Bansal|first2=A.|last3=Mangalalampally|first3=R. K.|last4=Singha Roy|first4=K.|last5=Teotia|first5=S. S.|title=Dynamically Triggered Events in a Low Seismically Active Region of Gujarat, Northwest India, during the 2012 Mw 8.6 Indian Ocean Earthquake|journal=Bulletin of the Seismological Society of America|date=2022|volume=112|issue=4|pages=1908–1920|issn=0037-1106|doi=10.1785/0120210142|bibcode=2022BuSSA.112.1908D|s2cid=248768288}}
• {{citation|title=Successful monitoring of the 11 April 2012 tsunami off the coast of Sumatra by Indian Tsunami Early Warning Centre|last1=Kumar|first1=T. S.|last2=Nayak|first2=S.|last3=Kumar|first3=Ch. P.|last4=Yadav|first4=R. B. S.|last5=Kumar|first5=B. A.|last6=Sunanda|first6=M. V.|last7=Devi|first7=E. U.|last8=Kumar|first8=N. K.|last9=Kishore|first9=S. A.|last10=Shenoi|first10=S. S. C.|journal=Current Science|year=2012|volume=102|issue=11|pages=1519–1526|jstor=24084760}}
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• {{commons category-inline}}
• [http://wikimapia.org/#lat=2.3467994&lon=93.072485&z=7&l=0&m=b Satellite View at Wikimapia.org]
• [http://www.isn.bosai.go.jp/events/20120411083834/index.html Preliminary source parameters obtained by automatic analysis – 2012/04/11 08:38 Off West Coast of Northern Sumatra] – International seismic network, NIED, Japan
• [https://www.sciencedaily.com/releases/2014/03/140311124319.htm After major earthquake, silence: Dynamic stressing of a global system of faults results in rare seismic silence] – Science Daily
• [https://www.sciencedaily.com/releases/2012/09/120926153028.htm Rare great earthquake in April triggers large aftershocks all over the globe] – Science Daily
• {{EQ-isc-link|600860404}}

{{Earthquakes in 2012}}

{{Earthquakes in Indonesia}}

Category:2012 in Indonesia

Category:Earthquakes in Indonesia

Category:Tsunamis in Indonesia

Indian Ocean earthquakes

Category:2012 disasters in Indonesia

Category:2010s in Aceh

Category:History of the Indian Ocean

Category:April 2012 in Indonesia

Category:Supershear earthquakes

Category:Earthquake clusters, swarms, and sequences

Category:Earthquakes in Sumatra