WASHINGTON — The federal and state governments need to improve warning systems before a deadly tsunami strikes the West Coast, a new study says.

While modern technology is able to detect the formation of a tsunami fairly quickly, the United States lacks a robust warning system and detailed knowledge of the impact giant waves could have on coastal areas, the Government Accountability Office says.

In a report issued yesterday, the GAO, the investigative arm of Congress, warns that false alarms may have lulled West Coast residents into an unjustified sense of security. Sixteen tsunami warnings issued since 1982 were not followed by destructive waves on U.S. shores, the report says, "potentially causing citizens to ignore future warnings."

Monitoring for the U.S. West Coast is handled by a tsunami center in Alaska.

(The Pacific Tsunami Warning Center in 'Ewa Beach monitors conditions in Hawai'i, most countries in the Pacific and all other U.S. interests in the Pacific outside of Alaska and the West Coast, according to the center's Web site.)

The report urges that the National Oceanic and Atmospheric Administration develop "loss estimation" software for tsunamis similar to that available for hurricanes or floods, so officials can predict how severe a potential strike could be.

The stakes are high, the report notes. While the United States has not been hit by a severe tsunami in more than four decades, experts say another destructive Pacific-wide tsunami is all but inevitable.

The report was issued 18 months after the 2004 Indian Ocean tsunami, which killed more than 216,000 people in 12 countries. U.S. Sen. Dianne Feinstein, D-Calif., who requested the report, said it indicates that California and other states are still at risk of a catastrophic tsunami, "and we are ill-equipped to deal with the threat."

The United States needs a warning system that can protect its most vulnerable communities, as well as software to determine where a tsunami is most likely to hit and do the most damage, Feinstein said.

"We've seen the danger. Now is the time to respond," she said.

Rep. David Wu, D-Ore., said programs focused on local warning systems and educating the public are key to protecting against a tsunami. "We cannot prevent earthquakes and tsunamis, but we can prepare for them and ensure the citizens of our coastal communities are safe and secure," Wu said.

"After witnessing the devastation following the (Indian Ocean) tsunami, there is no excuse for the federal government to be this far behind on coastal preparedness and making sure Americans have enough time to get to safety," added Sen. Maria Cantwell, D-Wash.

Cantwell called for the House to approve a Senate-backed bill aimed at improving tsunami detection and warning systems; providing communities with tsunami preparedness tools; and developing inundation maps for at-risk areas.

Congress appropriated more than $17.2 million last year to enhance tsunami warnings and protection, including repair of malfunctioning tsunami-detection buoys.