What happened and what's next?

摘要

The huge earthquake of 26 December 2004 and ensuing tsunami were caused by a submarine rupture running from offshore Aceh, Indonesia, to the Andaman Islands. A clearer picture of events is starting to emerge. As the human drama of the Aceh-Andaman earthquake and tsunami unfolded in the last days of 2004, laymen and scientists began scrambling to understand what had caused these gigantic disturbances of Earth's crust and seas. One of the earliest clues was the delineation, within just hours of the mainshock, of a band of large aftershocks arcing 1,300 km from northern Sumatra almost as far as Myanmar (Burma)1. This seemed to signal that about 25% of the Sunda megathrust, the great tectonic boundary along which the Australian and Indian plates begin their descent beneath Southeast Asia, had ruptured. In less than a day, however, analyses of seismic'body'waves were indicating that the length of the rupture was only about 400 km.