Earthquake off Sumatra 2012

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Earthquake off Sumatra
Earthquake off Sumatra 2012 (Indian Ocean)
Bullseye1.svg
date April 11, 2012
Time 08:38:38 UTC (14:38:38 local time )
Magnitude 8.6  M W
depth 10 km
epicenter 2 ° 20 '53 "  N , 93 ° 4' 19"  E Coordinates: 2 ° 20 '53 "  N , 93 ° 4' 19"  E
(431 km from Banda Aceh )
country BangladeshBangladesh Bangladesh India Indonesia Malaysia Singapore Sri Lanka Thailand
IndiaIndia 
IndonesiaIndonesia 
MalaysiaMalaysia 
SingaporeSingapore 
Sri LankaSri Lanka 
ThailandThailand 
Tsunami Yes


The 2012 earthquake off Sumatra was a major earthquake that occurred on April 11, 2012 at 2:38 p.m. local time (8:38 a.m. UTC ) off the coast of Sumatra in the Indian Ocean. The Geoforschungszentrum Potsdam determined a moment magnitude of 8.6 and a depth of 10 km. The earthquake was the eleventh strongest earthquake since 1900.

Tectonic overview

The earthquake of April 11th with a magnitude of 8.6 M w off the west coast of the northern part of the Indonesian island of Sumatra occurred as a result of leaf displacement within the oceanic lithosphere of the Indo-Australian plate . The center of the earthquake was about 100 km southwest of the main subduction zone, which forms the border between the Indo-Australian plate and the Sunda plate off the coast of Sumatra . In this area the Indo-Australian plate moves at a speed of about 52 mm per year in relation to the Sunda plate in a north-northeast direction.

Large leaf-displacement earthquakes are not uncommon in this region of the Indo-Australian plate. Since the Sumatran-Andaman earthquake of December 2004 with a magnitude of 9.1 M w , in which a 1300 km long segment of the Sumatran megathrust was torn open, three major leaf displacements have occurred in the vicinity of the center of the earthquake on April 11th . These happened on April 19, 2006 (M w = 6.2), on October 4, 2007 (M w = 6.2) and on January 10, 2012 (M w = 7.2). In all three cases the mode of displacement was similar. The focus mechanisms of the three earlier earthquakes and the two major earthquakes of April 11th are consistent with each other and imply that each of the earthquakes could have occurred as a result of a left-hand leaf displacement along a north-northeast trending or a right-hand leaf displacement along a west-northwest trending fracture . These two different orientations are possible under the same tectonic stress field; Blade displacement faults that are at right angles to one another and are compatible with the same area of ​​tension are called “complementary breaks”. Possibly breaks in both orientations were involved in the recent earthquake activity.

Effects of the quake

As a result of the earthquake and the strong aftershock with a magnitude of 8.2 M w , the two affected plates shifted by around 21 m against each other - in the most popular blade shift, the San Francisco earthquake of 1906 , the two sides faced each other of the San Andreas Trench moved about 4.5 m against each other. In terms of magnitude, the quake is the eleventh strongest earthquake since 1900 and at the same time the strongest ever recorded earthquake with a blade shift, but there is debate among geophysicists as to whether the Assam earthquake in 1950 was equally strong.

Tsunami warning

The Pacific Tsunami Warning Center initially issued a tsunami warning for the 28 states bordering the Indian Ocean, but canceled it for most states and areas about three hours after the earthquake.

Tsunami readings
place Coordinates Time (UTC) amplitude period
DART buoy 23401 8.9N 88.5E 09:56 0.03 m 06 min.
Meulaboh , Indonesia 4.1N 96.1E 10:07 1.06 m 12 min.
Sabang , Indonesia 5.8N 95.3E 10:10 0.36 m 06 min.
Tellukdalam , Indonesia 0.6N 97.8E 10:44 0.22 m 14 min.
Coconut Islands , Australia 12.1S 96.9E 11:02 0.08 m 18 min.
Enggano , Indonesia 5.3S 102.3E 11:04 0.12 m 04 min.
Trincomalee , Sri Lanka 8.6N 81.2E 11:29 0.06 m 16 min.
Ko Taphao Noi , Thailand 7.8N 98.4E 11:43 0.05 m 06 min.
Padang , Indonesia 1.0S 100.4E 12:08 0.09 m 34 min.
Gan , Maldives 0.7S 73.2E 12:12 0.03 m 48 min.
Malé , Maldives 4.2N 73.5E 12:23 0.19 m 06 min.
Hanimaddhoo , Maldives 6.8N 73.2E 12:35 0.25 m 06 min.
Source: Pacific Tsunami Warning Center

Reactions

Due to its magnitude, the earthquake was felt in large parts of South Asia and Southeast Asia, for example in the Indian cities of Chennai , Bangalore , Kochi , Bhubaneswar and Kolkata , on the west coast of the Malay Peninsula between Penang and Kuala Lumpur , in Colombo in Sri Lanka and on the Maldives, Singapore, Bangladesh, Burma, Vietnam and Thailand.

Aftershocks

In addition to several small quakes, an unusually severe aftershock with a magnitude of 8.2 occurred at 10:43:09 UTC about 250 km away.

New research results

In December 2016 new research results were published by scientists from the “Institut du Physique du Globe”. The earthquake region is therefore in the Wharton Basin. Strong soil deformations were detected there. The collision of the Indian plate with the Eurasian plate causes the Indian plate to rotate. At the same time, the Australian continent is migrating towards Indonesia. These slow plate shifts cause the ocean floor in the Wharton Basin to stretch and tear. The researchers fear further strong earthquakes in this region.

Web links

See also

Individual evidence

  1. ↑ a b Indian Ocean tsunami alert lifted after Aceh quake . BBC News. April 11, 2012. Retrieved April 11, 2012.
  2. ↑ Stove solution of the GEOFON network
  3. ↑ a b Scientists: Magnitude-8.6 Indonesia jolt was unusually large for a strike-slip quake (English) . In: Winnipeg Free Press , Canadian Press, April 11, 2012. Retrieved April 12, 2012. 
  4. ↑ M8.6 - off the west coast of northern Sumatra - Summary ( English ) United States Geological Survey. Retrieved April 11, 2011.
  5. ↑ Tsunami Bulletin Number 003 from 10:14 am UTC ( Memento of the original from April 13, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.tsunami.gov
  6. ↑ Tsunami Bulletin Number 005 from 11:51 a.m. UTC
  7. ^ PTI: News: Tremors across the eastern coast; people evacuated from Andamans (English) , The Hindu . April 11, 2012. 
  8. ↑ 8.6 earthquake hits Aceh, tsunami alert issued (Update) (English) . In: Thesundaily.my , April 11, 2012. 
  9. ↑ Large Aceh quake triggers Indian Ocean tsunami warning - Tremor felt in Colombo | Independent Television Network News ( English ) In: Itnnews.lk . April 11, 2012. Retrieved April 11, 2012.
  10. ^ Strong earthquake in Sumatra slightly felt in Yangon - Xinhua ( English ) Xinhua. April 11, 2012. Retrieved April 12, 2012.
  11. ↑ Focus solution of the aftershock
  12. ↑ Indian Ocean: further earthquakes feared