Echoes of the tsunami quake

摘要

While the world was gripped by the devastation wrought by the Indian Ocean tsunami on 26 December last year, the Sumatra-Andaman earthquake which triggered it was almost lost in the background. Now, astounding facts are emerging about the biggest quake to rock the Earth in the past few decades: it lasted longer, spread farther, and triggered the most distant and intense secondary quakes ever recorded. It also shook the Earth all over and our planet is still ringing from the shock. The tsunami-causing quake and the major Sumatra temblor it spawned on 28 March are the largest recorded since the advent of modern digital instruments. These can measure both the huge ground motions from the main quakes and the tiny movements from aftershocks. To make sense of what happened, researchers also used satellite measurements of changes in ocean height and readings from a network of GPS receivers that recorded subtle movements of the Earth's crust.