What happened
On 26 December 2004 the subduction zone along Sumatra and the Andaman Islands ruptured over about 1,300 kilometres, and the seafloor rose by several metres. Tsunami waves hit Aceh province within minutes and, over the following hours, Thailand, Sri Lanka, India, the Maldives and the east coast of Africa. At the time there was no tsunami warning system in the Indian Ocean. About 230,000 people died and millions lost their homes. After the disaster an international warning system for the Indian Ocean was established.
How to read these data
Magnitude measures the energy released at the focus: each step is about 32 times more energy, so an M 9 earthquake releases about a thousand times more energy than an M 7. Its effects, however, also depend on focal depth, distance to cities, ground conditions and building quality – a shallow M 7 beneath a city can be deadlier than a deep M 8 under the ocean.
Data: USGS ComCat (official20041226005853450_30) · Wikipedia (pl) · Wikipedia (en)