Scientists at the United States space agency NASA say they could be on the verge of a breakthrough in their efforts to forecast earthquakes.
Researchers say some of the biggest earthquakes, such as the recent one in China, seem to be preceded by disturbances high up in the earth's atmosphere.
They think rocks which are about to break become positively charged with electricity at the earth's surface.
The electrical effect is then transferred 100 kilometres into the ionosphere, where it can be picked up by satellites.
-BBC
