Researchers estimate total energy and local impact of the 2011 Japan tsunami
Aug. 22, 2012
Contact: Lauren Koellermeier, 206-526-6810
The March 11, 2011, Japan tsunami generated about 3 petajoules of energy, according to a new NOAA study. That’s enough to power New York City for seven days or the entire country of Canada for about two and a half hours, they estimate. The tsunami, generated by a 9.0 magnitude earthquake, killed more than 15,000 people and caused damage in excess of $300 billion, according to a Japanese government estimate.
The study, the first to estimate total energy of a tsunami from measurements made in real time during the tsunami propagation, was published earlier this month in the Journal of Geophysical Research – Oceans.
In a companion paper published in Pure and Applied Geophysics, scientists report that when they used the new energy estimate in tsunami computer models, the model results matched actual tsunami flood levels along the entire coastline of Japan with high accuracy (85.5 percent).
These studies were conducted by by researchers at the NOAA Pacific Marine Environmental Laboratory (PMEL) in Seattle and the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) at the University of Washington. JISAO is a collaboration between NOAA and the University of Washington.
The results of these studies will help scientists to further improve the forecast system they use to predict the size, direction, and arrival times of future tsunamis. NOAA’s tsunami warning centers use this system to issue warnings when a U.S. coast is threatened by an approaching tsunami. NOAA’s DART buoys (Deep Ocean Assessment and Reporting of Tsunamis), developed by PMEL scientists, are an essential part of this system. This technology, when fully implemented, can provide accurate flooding forecasts for nearby coastal areas within 30 minutes of the earthquake.
The DART buoy network, which was expanded following the December 2004 Indian Ocean tsunami disaster, enabled NOAA scientists to estimate the total energy in the Japan tsunami directly from DART buoy measurements collected during the tsunami propagation. Deployment of more buoys closer to coastal seismic zones will enable faster energy estimates within minutes of an earthquake, a crucial time window for forecasting tsunami impacts at shorelines closest to an earthquake.
Historically, scientists used earthquake magnitudes as indicators of tsunami size, however this method produces large uncertainties. Using deep-ocean pressure measurements at DART moorings allowed scientists to estimate the total energy transmitted by tsunami waves, painting a much better picture of actual tsunami wave activity. The 2011 Japan tsunami was the first, and the largest, tsunami for which deep-ocean data was available so close to the earthquake source. This test validated NOAA’s tsunami forecast system at all three stages, generation, propagation and inundation, of an evolving tsunami along hundreds of miles of coastline closest to the earthquake.
“The results of this study will provide important guidelines to improve the new tsunami forecast system, to provide more timely and accurate tsunami forecasts for the next event,” said Liujuan Tang, Ph.D., a JISAO tsunami modeler and lead author of the Journal of Geophysical Research study.
“Validation of model tsunami flooding estimates is an important step toward developing local tsunami flooding forecast capability, which is critical for addressing potential tsunami impacts in Pacific Northwest coastal areas.” added JISAO researcher Yong Wei, Ph.D., lead author of the Pure and Applied Geophysics paper.
Data recorded by the DART buoys closest to the March 11, 2011, earthquake off the coast of Japan also allowed scientists to pinpoint the location where the tsunami started – an area of about 11,500 square miles (30,000 square kilometers) along 248 miles (400 kilometers) of the Japan Trench.
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On the Web:
NOAA Pacific Marine Environmental Laboratory: http://www.pmel.noaa.gov
Joint Institute for the Study of the Atmosphere and Ocean: http://jisao.washington.edu
NOAA Center for Tsunami Research: http://nctr.pmel.noaa.gov
NOAA Pacific Tsunami Warning Center: http://ptwc.weather.gov
NOAA West Coast and Alaska Tsunami Warning Center: http://wcatwc.arh.noaa.gov