New York (PTI): Geophysicists from Britain and China have developed a new methodology to seismic monitoring that could help forecast the time, size and sometimes even the location of earthquakes.

The new method exploits a phenomenon called shear-wave splitting, in which seismic 'shear' waves travelling through rocks are split into two components, which vibrate parallel and perpendicular relative to microscopic cracks, according to a report published in Nature.

These two shear wave components travel through the ground at different speeds, and so reach detectors at different times.

The alignment of these microscopic cracks reflects the amount of stress in the Earth's crust. The more stress, the more the cracks are aligned, and the bigger the gap between the two waves' arrival.

So far efforts to predict the tremors have proved futile.

In the past, Nature says researchers have gauged the build-up of strain in earthquake zones indirectly, by looking at satellite maps of surface ground movement. But this gives only a rough idea of the stress changes deeper down, where earthquakes originate.

Stresses have also been monitored directly at fault lines, but such localized data doesn't show when and where slippage will occur.

The researchers' evidence, the report says, suggests that they could perhaps issue an hour's warning before a small quake and months before a big one. Their work is described in Geology.