Which 2004 earthquake off Sumatra triggered a devastating Indian Ocean tsunami?

The 2004 Sumatra–Andaman earthquake triggered the devastating Indian Ocean tsunami.

The undersea megathrust earthquake occurred on 26 December 2004, when the India Plate subducted beneath the Burma Plate near Sumatra. Its rupture extended for roughly 1,300 kilometres, abruptly lifting parts of the seafloor and displacing enormous volumes of seawater.

The resulting tsunami reached coastlines around the Indian Ocean, including Indonesia, Sri Lanka, India, Thailand, and East Africa. More than 200,000 people died, making it one of the deadliest natural disasters in recorded history.

It is often called the 2004 Indian Ocean earthquake or the Sumatra–Andaman earthquake. The tsunami was not caused by ordinary tidal action; it resulted from sudden seafloor movement during the earthquake.