The Powerful Sumatra-Andaman Islands Earthquake

Explanation: December's 9.0 earthquake has likely shortened Earth's day by about three microsecond s 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 the year 1900 and triggered tsunami s that tragically killed over 250,000 people in nearby coastal regions. In the above map , the yellow star indicates the location of the main earthquake , while circles show the locations of large aftershocks . The Sumatra - Andaman Islands 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 .