One frame of the homemade video shows a tourist caught in the first of six tsunamis as they rush toward the hut. … (+)
AFP (via Getty Images)
At 7:58 a.m. local time on December 26, 2004, an earthquake with a moment magnitude of Mw 9.1 to 9.3 destroyed more than 1,500 kilometers of ocean floor off the west coast of Sumatra, Indonesia.
This was the third strongest earthquake ever recorded, after Chile in 1960 (Mw 9.5) and Alaska in 1964 (Mw 9.2). The earthquake started on the Sumatra fault, a fault system associated with the subduction of the Indian plate beneath the Sunda plate. The earthquake propagated northward along the fault for about 20 minutes. It takes 8 to 10 minutes to travel the entire fault, making it the longest length and duration of any event of its kind ever recorded.
The rupture of the fault created a new cliff approximately 20 meters (65 feet) high on the ocean floor, which caused water movement and a series of six tsunamis that spread eastward to Indonesia, Thailand, and westward to Sri Lanka, India, and moved towards Africa. — eventually reaching the Atlantic and Pacific Oceans.
More than 126,000 people have been killed or injured, and 94,000 people remain missing in 14 countries, according to official UN figures. The tsunami displaced more than 1.5 million people and destroyed more than 100,000 homes in Indonesia’s Aceh province, the closest region to the epicenter.
The impact of the disaster was further exacerbated by the fact that there was no tsunami early warning system in the Indian Ocean before the 2004 tsunami. There were no seismic observatories covering the entire region, and no communication systems were in place to immediately alert coastal residents.
The 2004 earthquake triggered more than 6,000 aftershocks in the first decade, including two with Mw 8.6 and Mw 8.4, which destroyed much of the remaining Sumatra subduction zone. The seismic gap, where no earthquakes have occurred to date, highlights the need for greater preparedness in the region as tectonic tensions continue to rise.
Advances in earthquake and tsunami science since 2004 have facilitated improvements in coastal protection, early warning systems, and risk communication. However, challenges persist, especially in areas close to the tsunami source. Here, the warning time between the detection of an earthquake and the first tsunami reaching the coast can be just a few minutes.
Future communication efforts must help the public understand that no warning system is perfect and that it is safest to evacuate if there are signs of a potential tsunami.
The study, “Insights into tectonic movements since the 2004 Indian Ocean earthquake and tsunami,” is published in the journal nature reviews Earth & Environmental and can be viewed online here.
