Students evacuate as they reach higher grounds after a tsunami warning released by the government during a tsunami drill part of a disaster awareness programme at a school in Banda Aceh, Indonesia. December 2015 marks the 11th anniversary of the 2004 Indian Ocean Tsunami, which struck on Dec 26, 2004, triggered by a 9.2 earthquake off the west coast of northern Sumatra, killing an estimated 230,000 people in 13 countries.