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Fall/Winter 2010 Vol. 10 Number 3

Table of Contents

A Sea Change

Is U.S. Prepared for a Major Tsunami?

©Teofilo Olivieri/

The devastating tsunami that swelled in the Indian Ocean in 2004 killing approximately 200,000 people was a wake-up call to the dangers of a similar event striking U.S. shores. Often thought of as massive tidal waves, tsunamis are series of waves created by seafloor displacements that move rapidly onshore and can cause extensive flooding of coastal communities.

A recent report from the National Research Council found that the nation's ability to detect and forecast tsunamis has improved in the last six years, but many U.S. coastal areas still remain at great risk, especially for tsunamis that leave little time for warning and evacuation.

In recorded U.S. history, tsunamis have taken lives in Hawaii, Alaska, Puerto Rico, American Samoa, the Virgin Islands, California, and Oregon. They can be triggered by a variety of geologic events, most commonly by earthquakes and landslides, but volcanic eruptions or meteorite impacts can also cause them. The threat of a potentially catastrophic tsunami on U.S. soil looms large particularly in seismically active regions.

"If a large earthquake near shore triggers a tsunami, it could reach the coast within minutes, allowing hardly any time to disseminate warnings and for the public to react," said John Orcutt, chair of the committee that wrote the report. "Education and preparation are necessary to ensure that people know how to recognize natural cues -- such as earthquake tremors or receding of the waterline -- and take appropriate action, even if they do not receive an official warning."

The report finds many enhancements have been made due to U.S. tsunami-related efforts, including an increase in the amount and quality of hazard and evacuation maps and the expansion of the Deep-Ocean Assessment and Reporting of Tsunamis (DART) sensor network that estimates the size of tsunamis. Improvements have also been made in coastal sea-level stations and the Global Seismic Network operated and maintained by the U.S. Geological Survey and the National Science Foundation. Moreover, various states have evaluated select tsunami-prone communities and initiated several education and awareness efforts.

However, in addition to improving detection and forecasting networks, the committee stressed that a comprehensive tsunami program also requires risk assessments, public education, and a well-coordinated response -- areas where more progress in the U.S. program will be needed. To gauge how to prioritize such efforts, the report recommends completing a national tsunami risk assessment that characterizes the hazards, inventories the threatened populations and assets, measures the preparedness and ability of individuals and communities to evacuate, and estimates expected losses.

The report also calls for improving communications and coordination among the two federal Tsunami Warning Centers (TWCs) in the Pacific, emergency managers, media, and the public. The TWCs monitor seismic activity and sea levels to detect tsunamis and warn emergency managers.

Although the TWCs are designed as backups for each another, the organizational model of two centers is problematic. The separate warnings have conflicted, causing confusion among the media, local officials, and the public. Residents of American Samoa walk through high water and debris caused by a 2009 tsunami, photo by Casey Deshong/FEMAFor example, in June 2005 the Pacific Northwest received seemingly contradictory messages from the two centers. Those in northern California who received both messages thought the all-clear message from the Hawaii center canceled the tsunami warning from the Alaska center. The committee recommended that message content be improved or the two TWCs release one message that includes information for all areas under their responsibility.

Additionally, the report proposes that the TWC organizational structure be evaluated -- including deciding whether multiple TWCs should issue a single message or a single, centrally managed center should be created, similar to the National Hurricane Center. --  Jennifer Walsh

Tsunami Warning and Preparedness: An Assessment of the U.S. Tsunami Program and the Nation's Preparedness Efforts. Committee on the Review of the Tsunami Warning and Forecast System and Overview of the Nation's Tsunami Preparedness, Ocean Studies Board, Division on Earth and Life Studies (2010, approx. 350 pp.; ISBN 0-309-13753-5; available from the National Academies Press, tel. 1-800-624-6242; $47.00 plus $5.00 shipping for single copies).

The committee was chaired by John A. Orcutt, professor, Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, La Jolla, Calif.; and vice chaired by Martha A. Grabowski, professor and director of the information systems program, Le Moyne College, Syracuse, N.Y., and Research Professor of Decision Sciences and Engineering Systems, Rensselaer Polytechnic Institute, Troy, N.Y. The study was funded by the National Oceanic and Atmospheric Administration; University of Alaska, Fairbanks; and National Academy of Sciences.

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