What earthquake caused the Indian Ocean tsunami of 2004?

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Aceh, Indonesia: tsunami aftermath — tsunami Aftermath of the December 2004 tsunami in Aceh, Indonesia.

The 2004 Indian Ocean tsunami was triggered by a massive undersea earthquake that occurred on December 26, 2004. This seismic event, which registered a magnitude of 9.1, struck off the coast of the Indonesian island of Sumatra.12

The displacement caused by the quake generated a tsunami—a series of immense ocean waves—that traveled across the Indian Ocean over the following seven hours. The waves devastated coastal regions in 15 countries, resulting in one of the deadliest natural disasters in recorded history.12