In the wake of February’s earthquake in Chile, a NASA-led team successfully tested elements of a prototype tsunami prediction system.
Y Tony Song of NASA’s Jet Propulsion Laboratory used real-time data from NASA’s Global Differential GPS (GDGPS) system to predict the effects of the magnitude 8.8 quake.
The network combines global and regional real-time data from hundreds of GPS sites and estimates their positions every second. It can detect ground motions as small as a few centimeters, says NASA.
“This successful test demonstrates that coastal GPS systems can effectively be used to predict the size of tsunamis,” said Song. “This could allow responsible agencies to issue better warnings that can save lives and reduce false alarms that can unnecessarily disturb the lives of coastal residents.”
Song’s team concluded that the Chilean earthquake – the fifth largest ever recorded – would generate a moderate, or local, tsunami.
That prediction was later confirmed using sea surface height measurements from the joint NASA/French Space Agency Jason-1 and Jason-2 altimetry satellites.
“The value of coordinated real-time observations from precision GPS, satellite altimetry and advanced Earth models has been demonstrated,” said John LaBrecque, manager of the Solid Earth and Natural Hazards program in the Earth Science Division of NASA’s Science Mission Directorate in Washington.
Song’s prediction method relies on data from coastal GPS stations, along with information about the local continental slope.
Previous tsunami models presume a tsunami’s power is determined by how much the seafloor is displaced vertically, but Song’s theory says horizontal motions of a faulting continental slope also contribute to a tsunami’s power by transferring kinetic energy to the ocean.
Song calculated the Chilean tsunami’s source energy, ranking it as moderate: a 4.8 on the system’s 10-point scale. His conclusion was based on the fact that the ground motion detected by GPS indicated the slip of the fault transferred fairly little kinetic energy to the ocean.