New Light on Deep Earthquakes; Our Ever Changing Earth; Special Editions; by Harry W. Green II; 9 Page(s)

On June 7, 1994, a great earthquake rumbled through Earth's mantle more than 600 kilometers beneath Bolivia. It was the largest earthquake ever recorded at such depths. The tremors were felt as far away as Toronto. No other quake in history had been felt so far from its epicenter.

The event was truly spectacular and yet paradoxical as well. Although deep earthquakes are as regular as clockwork, in theory they should be impossible. Indeed, the very existence of deep earthquakes has teased geophysicists since their discovery in 1927. In 1989 my colleagues and I began to unravel the solution to this puzzle in the laboratory. This article gives an account of that discovery, the new theory of earthquakes that has flowed from it, and recent developments in our understanding.