The approximate rupture length of the 2004 Indian Ocean earthquake was 1,600 kilometers. That enormous rupture unfolded along the Sunda subduction zone, where the Indian Plate is forced beneath the overriding Burma microplate near Sumatra and the Andaman and Nicobar Islands.
The earthquake began off the coast of Aceh on December 26, 2004, and the rupture propagated northward in stages over several minutes. In the southern section, the fault slipped by about 15 meters in places. The seafloor rose by several meters, displacing an estimated 30 cubic kilometers of water and generating the devastating Indian Ocean tsunami.
The 1,600-kilometer figure describes the length of fault surface that slipped, not the distance traveled by the tsunami. That distinction is a common source of confusion: tsunami waves crossed the Indian Ocean and affected coastlines thousands of kilometers from the epicenter, while the earthquake’s rupture itself extended along the plate boundary from northern Sumatra toward the Andaman region. Its exceptional length helped make the event one of the largest earthquakes ever instrumentally recorded.