Many coastal areas of the United States are at risk from tsunamis. Since 1800, tsunamis have taken lives in Hawaii, Alaska, Puerto Rico, American Samoa, the Virgin Islands, California, and Oregon. Tsunamis happen rarely enough to allow a false sense of security, but when they do occur there may be just minutes or hours for people to reach a safer location.
The catastrophic 2004 tsunami in the Indian Ocean provided the impetus for legislation to expand U.S. tsunami warning capabilities (P.L. 109-13). This was followed by the Tsunami Warning and Education Act of 2006 (P.L. 109-424), which asked the National Oceanic and Atmospheric Administration (NOAA) and the National Tsunami Hazard Mitigation Program (NTHMP) to strengthen the nation’s existing tsunami detection, warning, education, and preparedness efforts. In the 2006 law, Congress requested the National Academy of Sciences (NAS) to review progress toward the nation’s ability to detect and forecast tsunamis. The NAS expanded the study’s scope to include assessment of the nation’s ability to reduce tsunami losses by educating and preparing the American public.
In this report, the study committee finds that the nation has made progress in several areas since 2004. At the federal level, NOAA has improved the ability to detect and forecast tsunamis by expanding the sensor network (specifically the Deep-ocean Assessment and Reporting of Tsunamis, or DART, buoys). Other federal and state activities to increase tsunami safety include: improvements to tsunami hazard and evacuation maps for many coastal communities; vulnerability assessments of some coastal populations in several states; and new efforts to increase public awareness of the hazard and how to respond.
Despite these advances, many coastal communities in the United States still face challenges in responding to a tsunami that arrives in less than an hour after the triggering event. If the source were so close to shore that only minutes were available before the tsunami reached the coast, the public would need to recognize natural cues—mainly, ground shaking from the tsunami-triggering earthquake—and know to evacuate even without official warnings. If the nearby source earthquake is weak, or if the tsunami takes more than an hour or two to reach a coast, technological tsunami detection and forecasting could give advance warning for evacuation of coastal areas but seamless coordination between the two Tsunami Warning Centers and clear communications to local officials and the public would be required for a timely and effective response.
The current organizational structure of the two Tsunami Warning Centers has not been optimized for coordinated, clear communication of tsunami warnings. The two centers have different areas of responsibilities; are managed by different regional offices; use different technology; have separate support and organizational cultures; and do not provide functional redundancy. As a result, the public could receive conflicting warning messages from the two centers. In addition, the content of the warning messages is inconsistent with social science
findings on the composition and delivery of effective warning messages, especially with regard to the importance of delivering a consistent and clear message when there are multiple information sources. A range of remedies is discussed in the report, from harmonizing message content to changing the organizational structure, such as merging the centers.
Previous reports have called for a national tsunami risk assessment to allocate funding based on the number of people, their vulnerability, or economic assets at risk. The committee endorses this concept and finds that progress is slow toward the completion of such an assessment and is limited by several factors:
incomplete knowledge of tsunami sources;
inconsistent access to high-quality bathymetric and topographic data;
differences in inundation modeling approaches and choice of source parameters for the same event between states; and
lack of vulnerability assessments that inventory the number, type, awareness, levels of preparedness, and evacuation potential of populations in tsunami-prone areas.
This report recommends stronger NOAA and NTHMP leadership in assessing tsunami sources, developing national guidelines and metrics for creating consistent evacuation maps, identifying vulnerable populations, and inventorying and evaluating education and preparedness efforts. Also, it is important to design effective interagency exercises, use professional emergency-management standards to prepare communities, and prioritize funding based on tsunami risk.
In addition, the report describes areas of research and development that would improve tsunami education, preparation, and detection:
metrics to assess progress in education and preparedness efforts;
inundation and forecast models that include an open validation and accreditation process, as well as post-event data validation;
improved reliability, station coverage, and operations of the newly deployed DART network;
periodic and comprehensive vulnerability assessments;
coordination for post-tsunami event reconnaissance; and
new tsunami detection techniques and analysis.
Regular, independent scientific review of the various elements of the tsunami program would be valuable in identifying and addressing research needs and in ensuring the effective implementation of new technologies and protocols.
Minimizing future losses to the nation from tsunamis requires persistent progress across the broad spectrum of efforts the report reviews: risk assessment, public education, government coordination, detection and forecasting, and warning-center operations. Sustained efforts in all these areas will be needed for communities to prepare for an event that may occur years to decades in the future, but only affords minutes or hours for people to respond.