Global positioning systems (GPS) may be used to provide accurate warning of a tsunami in just a few minutes after the earthquake onset, scientists say.         Researchers have demonstrated that by using GPS to measure ground deformation caused by a large underwater earthquake, they can warn of the resulting tsunami in just a few minutes after the quake.        

For the devastating Japan 2011 event, the team revealed that the analysis of the GPS data and issue of a detailed tsunami alert would have taken no more than three minutes.        

Most tsunamis, including those in offshore Sumatra, Indonesia in 2004 and Japan in 2011, occur following underwater ground motion in subduction zones, locations where a tectonic plate slips under another causing a large earthquake.        

To a lesser extent, the resulting uplift of the sea floor also affects coastal regions. There, researchers can measure the small ground deformation along the coast with GPS and use this to determine tsunami information.  

Image: People join hands facing the sea to mourn victims of the 2011 earthquake and tsunami, in Iwaki, Fukushima. |  Photograph: Reuters