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[SANTIAGO] Chile is set to become the first developing country to have a fully operational tsunami early-warning system that uses a satellite-based positioning system to provide alerts just minutes after an earthquake triggering a giant wave begins.
Such a system could have provided a warning just three minutes after the start of the March 2011 earthquake in Japan that caused the catastrophic tsunami — saving many lives, according to the authors of a paper published in Natural Hazards and Earth System Sciences last month (17 May).
Most tsunamis — including the Japanese one and those that struck Indonesia in 2004 and Chile in 2010 — are triggered by sea-floor motions caused by earthquakes in subduction zones, where one of the tectonic plates that form the planet's outer shell slips under another.
By placing GPS (Global Positioning System) instruments roughly every 40 kilometres along the coast to measure sea-floor deformation, they will be close to the epicentre of any future earthquakes. These instruments then send the raw data to a central station for calculating tsunami risk, the paper says.
The new method was developed by researchers at the GFZ German Research Centre for Geosciences in Potsdam.
Traditional tsunami early-warning systems for coastal regions exposed to subduction earthquakes use seismological information should be able to provide a warning five to ten minutes after an earthquake starts, but within that time limit they tend to underestimate the magnitude of large earthquakes and, thus, a tsunami's true impact on coastal areas, the paper says.
Andrey Babeyko, a GFZ researcher and one of the paper's authors, tells SciDev.Net that the method is best suited to places where earthquakes occur near to land.
"Natural conditions in Chile are much better than in Japan because the subduction zone is very close to the land," he says. "This means that information from GPS stations will get to the processing centre very fast and that the GPS will recognise and quantify offshore earthquakes much better."
He says that he visited Chile a month ago to start work with Sergio Barrientos, director of the Seismological Service at the University of Chile, on a project to upgrade the country's tsunami early-warning system.
"We will be installing GPS instruments that measure ground displacements that occur due to rupture," Barrientos tells SciDev.Net. Such movements occurred during the 2010 disaster.
"Monitoring these displacements in real time will enable us to estimate the characteristics of the earthquake that produced them as well as the resulting uplift of the ocean floor," he says. "With this information, we will be able to determine the tsunami-generating potential of the earthquake."
The installation of 130 coastal GPS sensors to complement Chile's existing seismological network will start later this year and take around two years, Barrientos adds.
Andreas Hoechner, another GFZ researcher and the paper's main author, tells SciDev.Net that each GPS sensor costs around US$20,000, excluding transmission and processing costs. He adds that reliable maintenance in remote areas, as well as getting data from stations to the warning centre when the shaking is too strong, could prove challenging.
Natural Hazards and Earth System Sciences doi: 10.5194/nhess-13-1285-2013 (2013)