The Sumatra-Andaman Islands Earthquake
December 26th, 2004
The 9.0 Sumatra-Andaman Islands earthquake of December 26, 2004, has likely shortened Earth's day by about three microseconds and may also have tweaked Earth's rotational wobble. The megathrust earthquake occurred as the Indian tectonic plate slid further beneath the Burma tectonic plate. The earthquake was the fourth most powerful since 1900 and triggered tsunamis that tragically killed over 250,000 people in nearby coastal regions. In the map, the yellow star indicates the location of the main earthquake, while circles show the locations of large aftershocks. This earthquake's effect on the Earth's rotation was sudden but much smaller than the accumulated effects of other surface events such as an El Nino.
-- U.S. Geological Survey