"State assessments of likely tsunami impacts on people and infrastructure have been limited, in part, due to a lack of tsunami loss estimation software, as exists for floods and other hazards," according to the report. "Although federal warning centers quickly detect potential tsunamis and issue warnings, false alarms and warning system limitations hamper their effectiveness."
According to the National Oceanic and Atmospheric Administration (NOAA), the areas most likely to be threatened by the effects of distant and local tsunamis are Hawaii, California, Oregon and Washington, while Alaska, Puerto Rico, and the U.S. Virgin Islands are threatened primarily by local tsunamis. Historically, risks to the East and Gulf coasts are relatively low.
Because inundation maps are the foundation for evaluating potential tsunami impacts on communities, map production has been a high priority for NOAA and the threatened states, the GAO said.
"However, progress on this front has been slow -- for example, Alaska has inundation maps for only five of 60 at-risk communities -- primarily because accurate maps are complex and costly for states to produce," according to the report.
To effectively prepare for a tsunami, state and local officials also need to assess the potential impacts of a tsunami on people and infrastructure, the GAO said.
However, while the Federal Emergency Management Agency (FEMA) has standardized computer software for estimating the likely human, structural and economic damages from natural disasters such as floods, hurricanes and earthquakes, no such tool exists for tsunamis, the GAO said.
That's one of the reasons California and Alaska haven't specifically assessed potential tsunami losses, while other at-risk areas have produced limited tsunami damage assessments, according to the report.
The GAO is recommending that NOAA work with FEMA and the U.S. Geological Survey (USGS) to create standardized tsunami loss estimation software.
In commenting on the report, the Department of Commerce, representing NOAA, agreed with the GAO's recommendations and indicated that steps will be taken to implement them. The Department of Homeland Security, representing FEMA, agreed with the recommendation that NOAA should work with FEMA and USGS to create standardized tsunami loss estimation software. However the department said that FEMA doesn't have the money for the software.