[9][10] 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).

[14] A back projection analysis of data collected by Hi-net, an observation network in Japan, found a complex pattern of four conjugate faults.

[17] The rupture was caused by ductile shear heating instability which is different from frictional failure and operates between 600–800 °C (1,112–1,472 °F), which corresponds to about the depths of 40–60 km (25–37 mi).

The serpentinization of oceanic lithosphere can lead to a low friction coefficient, but the reaction is possible only up to 400–500 °C (752–932 °F), which corresponds to the depth of about 25 km (16 mi).

[20] 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.

[25][26][27] Shaking was felt across the eastern coast of India including Chennai, Bangalore, Kochi, Bhubaneswar, Vizag and Kolkata.

[33] 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.

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).

[39] A seismologist from the British Geological Survey[40] said that the "tearing earthquake" displaced relatively little water and was therefore unlikely to cause a significant tsunami.

[41] 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.

[11] After the earthquake, the Indian National Centre for Ocean Information Services (INCOIS) issued a high-level tsunami warning for the Andaman and Nicobar Islands.

[43] Areas subject to warnings included Tamil Nadu, Andhra Pradesh and the Union Territory of Andaman and Nicobar Islands.

[45] The Ministry of Disaster Management and Human Rights (Sri Lanka) authorised an evacuation order[46] at 9:08 UTC advising people living near coastal regions to move to higher ground.

[11] As part of a risk mitigation measure, the Ceylon Electricity Board disconnected power supplies to coastal areas and railway control rooms.