Scientists in the United States believe they've found a way of spotting tsunamis as they cross the open ocean.
The National Oceanic and Atmospheric Administration, published in the journal Natural Hazards and Earth System Sciences, may lead to better ways of detecting the giant waves and getting people out of their way in time.
The research, which challenges previous theories that tsunamis cannot be seen in the open ocean, shows that they change the texture of the sea's surface in a way that can be tracked from space.
The study says that large tsunamis, anyway, stir up and darken the surface water along the wave's leading edge. The rougher water forms a shadow that can then be measured by satellites.
'Clear patterns in water' found with Boxing Day tsunami
The researchers went back and looked at satellite images of the Indian Ocean at the time when the December 2004 tsunami was heading towards the coasts of Thailand, Sri Lanka and elsewhere. They found clear patterns in the water.
Since the Boxing Day tsunami many governments have sought to establish an early-warning system of mid-ocean buoys that would detect such waves as they pass by. But such systems are imperfect, as buoys cannot be placed everywhere.
By the same token, the kind of satellites capable of tracking tsunamis do not cover all the world's seas.