NASA Demonstrates Tsunami Prediction System

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
Dwayne.c.brown@nasa.gov

News release: 2010-198 June 14, 2010

NASA Demonstrates Tsunami Prediction System

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2010-198&cid=release_2010-198

PASADENA, Calif. – A NASA-led research team has successfully demonstrated for the first time
elements of a prototype tsunami prediction system that quickly and accurately assesses large
earthquakes and estimates the size of resulting tsunamis.

After the magnitude 8.8 Chilean earthquake on Feb. 27, a team led by Y. Tony Song of NASA's Jet
Propulsion Laboratory in Pasadena, Calif., used real-time data from the agency's Global Differential
GPS (GDGPS) network to successfully predict the size of the resulting tsunami. The network,
managed by JPL, 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.

"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 by instruments,
would generate a moderate, or local, tsunami unlikely to cause significant destruction in the Pacific.
The tsunami's effect was relatively small outside of Chile.

Song's GPS-based prediction was later confirmed using sea surface height measurements from the
joint NASA/French Space Agency Jason-1 and Jason-2 altimetry satellites. This work was partially
carried out by researchers at Ohio State University, Columbus.

"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, published in 2007, estimates the energy an undersea earthquake transfers
to the ocean to generate a tsunami. It relies on data from coastal GPS stations near an epicenter, along
with information about the local continental slope. The continental slope is the descent of the ocean
floor from the edge of the continental shelf to the ocean bottom.

Conventional tsunami warning systems rely on estimates of an earthquake's location, depth and
magnitude to determine whether a large tsunami may be generated. However, history has shown
earthquake magnitude is not a reliable indicator of tsunami size. Previous tsunami models presume a
tsunami's power is determined by how much the seafloor is displaced vertically. 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.

The theory is further substantiated in a recently accepted research paper by Song and co-author Shin-
Chan Han of NASA's Goddard Space Flight Center, Greenbelt, Md. That study used data from the
NASA/German Aerospace Center Gravity Recovery and Climate Experiment (Grace) satellites to
examine the 2004 Indian Ocean tsunami.

When the Feb. 27, 2010, earthquake struck, its ground motion was captured by the NASA GDGPS
network's station in Santiago, Chile, about 235 kilometers (146 miles) from the earthquake's
epicenter. These data were made available to Song within minutes of the earthquake, enabling him to
derive the seafloor motions.

Based on these GPS data, Song calculated the tsunami's source energy, ranking it as moderate: a 4.8
on the system's 10-point scale (10 being most destructive). His conclusion was based on the fact that
the ground motion detected by GPS indicated the slip of the fault transferred fairly minimal kinetic
energy to the ocean.

"We were fortunate to have a station sufficiently close to the epicenter," said Yoaz Bar-Sever, JPL
manager of the GDGPS system. "Broad international collaboration is required to densify the GPS
tracking network so that it adequately covers all the fault zones that can give rise to large earthquakes
around the world."

For information about NASA and agency programs, visit: http://www.nasa.gov .

JPL is managed for NASA by the California Institute of Technology in Pasadena.

-end-

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