GPS data could speed up tsunami warnings

Faster tsunami warnings could be issued by using Global Positioning System (GPS) data alongside existing earthquake detection technology, scientists have found. GPS data — provided by a satellite navigation system — could help cut the time lag from 20 minutes to around three minutes, according to results presented at the American Geophysical Union meeting in the United States, last week (8 December).

Seismic instruments — on which current warning systems are based — can take a long time accurately to assess an earthquake's strength, because readings from several locations need to be analysed. However, GPS stations can measure large vertical drops in ground elevation — the factor responsible for tsunamis — in real time. This information, when added to preliminary seismic data from the same location, can determine the size — and likely effects — of the earthquake in a matter of minutes. All the technology is already in place in California and Japan, it is just a case of coordinating it, said Yehuda Bock, a researcher at the University of California, United States, who led the team. "There's a separation between [scientific] communities that we need to fix," he said.

Adding seismic instruments to GPS centres would be costly — perhaps around US$22,000 per station — but Bock has developed a method at a fraction of the cost. Attaching an accelerometer — a device that measures the vibration or change in motion of a structure — instead can be achieved for a few thousand dollars and has already been shown to work in the laboratory.

"It should work really well, where it works," said Andrew Newman of the Georgia Institute of Technology in United States. But, with only a few places with the necessary GPS and seismic technology and with small islands lacking the space for installing the instruments, he stressed that the system might not be suitable for everywhere. Only a small number of the roughly 1,200 GPS stations that exist in both Japan and the United States are close enough to seismic sensors to be used in the way that Bock proposes. His team has received funding to develop and test a prototype device, which could be in place within six months.

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