When the magnitude 9 earthquake struck Japan more than two years ago, there were 1,200 global positioning system (GPS) stations recording ocean-floor movement.

None was linked to that nation’s tsunami-warning system, which underestimated the full impact of the inundation that killed more than 18,000 people, left at least 350,000 homeless and caused meltdowns in three nuclear reactors.

Data from those GPS stations could have produced a more accurate warning within three minutes, including a better estimate of wave sizes and tremor magnitude, a team of European researchers has found.

Authorities in Japan did issue a warning within three minutes of the March 11, 2011, quake, but only for three nearby prefectures.

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“Japan has a very dense network of GPS stations, but these were not being used for tsunami early warning as of 2011. Certainly this is going to change soon,” said lead author Andreas Hoechner from the German Research Center for Geosciences.

A “GPS shield” that could warn people of tsunami threats has been a dream of disaster preparedness at least since the 2004 Indian Ocean tsunami that killed about 230,000 people.

The research team already proved that such a system was feasible. But the Japan quake, the most carefully measured seismic event in history, gave the researchers a wealth of data with which to test their system.

The researchers used 50 GPS stations closest to the quake’s epicenter, and produced a warning that closely correlates with the event’s measurements. Their work is published in Natural Hazards and Earth System Sciences, a publication of the European Geosciences Union.