[32] Indonesia lies between the Pacific Ring of Fire along the north-eastern islands adjacent to New Guinea, and the Alpide belt that runs along the south and west from Sumatra, Java, Bali, Flores to Timor.

As well as the sideways movement between the plates, the 2004 Indian Ocean earthquake resulted in a rise of the seafloor by several metres, displacing an estimated 30 km3 (7.2 cu mi) of water and triggering devastating tsunami waves.

[49] Because of its enormous energy release and shallow rupture depth, the earthquake generated remarkable seismic ground motions around the globe, particularly due to huge Rayleigh (surface) elastic waves that exceeded 10 mm (0.4 in) in vertical amplitude everywhere on Earth.

The surface waves can be clearly seen to reinforce near the antipode (with the closest seismic stations in Ecuador), and to subsequently encircle the planet to return to the epicentral region after about 200 minutes.

[57] Unlike data from tide gauges installed on shores, measurements obtained in the middle of the ocean can be used for computing the parameters of the source earthquake without having to compensate for the complex ways in which proximity to the coast changes the size and shape of a wave.

This rare sight reportedly induced people, especially children, to visit the coast to investigate and collect stranded fish on as much as 2.5 km (1.6 mi) of exposed beach, with fatal results.

[70] On Maikhao Beach in north Phuket City, Thailand, a 10-year-old British tourist named Tilly Smith had studied tsunamis in geography at school and recognised the warning signs of the receding ocean and frothing bubbles.

[71] John Chroston, a biology teacher from Scotland, also recognised the signs at Kamala Bay north of Phuket, taking a busload of vacationers and locals to safety on higher ground.

Footage showed evidence of back-flowing of the Aceh River, carrying debris and people from destroyed villages at the coast and transporting them up to 40 km (25 mi) inland.

The high fatality rate in the area was mainly due to lack of preparation of the community towards a tsunami and limited knowledge and education among the population regarding the natural phenomenon.

[83] The greatest run-up height of the tsunami was measured at a hill between Lhoknga and Leupung, on the western coast of the northern tip of Sumatra, near Banda Aceh, and reached 51 m (167 ft).

The quiet resort town of Khao Lak is located on a stretch of golden sandy beach, famed for its hotels overlooking the Andaman Sea and hilly rainforests.

Another amateur video, captured by a German family at beach level, showed the tsunami appearing as a white horizontal line in the distant horizon, gradually becoming bigger (bore-like), engulfing a jet skier and lifting two police boats.

[97] Velankanni, a coastal town with a Catholic Basilica and a popular pilgrimage destination was also one of the worst hit by the tsunami that struck at around 9.30 am on that Sunday, when pilgrims who were mostly from Kerala among others were inside the church attending the Malayalam Mass.

Kerala experienced tsunami-related damage in three southern densely populated districts, Ernakulam, Alappuzha, and Kollam, due to diffraction of the waves around Sri Lanka.

Inundation was observed, along the east coast of South Andaman Island, restricted to Chidiyatapu, Burmanallah, Kodiaghat, Beadnabad, Corbyn's Cove and Marina Park/Aberdeen Jetty areas.

The 71 casualties can be attributed to poor housing infrastructure and additionally, the fact that the coastal residents in the surveyed areas live on flat land along the coast, especially in the Irrawaddy Delta, and that there is no higher ground to which to evacuate.

[113][114] Tidal surges also occurred along the Western Australian coast that lasted for several hours, resulting in boats losing their moorings and two people needing to be rescued.

[citation needed] In addition to a large number of local residents, up to 9,000 foreign tourists (mostly Europeans) enjoying the peak holiday travel season were among the dead or missing, especially people from the Nordic countries.

Severe damage was inflicted on ecosystems such as mangroves, coral reefs, forests, coastal wetlands, vegetation, sand dunes and rock formations, animal and plant biodiversity and groundwater.

[145] The IWMI developed protocols for cleaning wells contaminated by saltwater; these were subsequently officially endorsed by the World Health Organization as part of its series of Emergency Guidelines.

[145] In addition to other forms of aid,[147] the Australian government sent ecological experts to help develop strategies for reef-monitoring and rehabilitation of marine environments and coral reefs in the Maldives, Seychelles and other areas.

[148] In response to the unprecedented situation, the United Nations Environment Programme (UNEP) worked with governments in the region to determine the severity of the ecological impact and how to address it.

[149] UNEP established an emergency fund, set up a Task Force to respond to requests for assistance from countries affected by the tsunami, and was able to mobilize and distribute approximately US$9.3 million for environmental recovery and disaster risk reduction between 2004 and 2007.

Such approaches to ecosystem-based disaster risk reduction appear to be most successful when local communities are closely involved as stakeholders throughout the process, and when careful attention is paid to the physical conditions of chosen sites to ensure that mangroves can thrive there.

[157] While the tsunami destroyed many of the boats vital to Sri Lanka's fishing industry, it also created a demand for fibreglass-reinforced plastic catamarans in the boatyards of Tamil Nadu.

[160] Both the earthquake and the tsunami may have affected shipping in the Malacca Straits, which separate Malaysia and the Indonesian island of Sumatra, by changing the depth of the seabed and by disturbing navigational buoys and old shipwrecks.

[171] Saudi cleric Muhammad Al-Munajjid attributed it to divine retribution against non-Muslim vacationers "who used to sprawl all over the beaches and in pubs overflowing with wine" during Christmas break.

On 30 December 2004, four days after the tsunami, Terra Research notified the India government that its sensors indicated there was a possibility of 7.9 to 8.1 magnitude tectonic shift in the next 12 hours between Sumatra and New Zealand.

[178] On further investigation, the India government learned that the consulting company Terra Research was run from the home of a self-described earthquake forecaster who had no telephone listing and maintained a website where he sold copies of his detection system.