A 7.7-magnitude earthquake on Monday set off a tsunami that leveled whole villages on the Mentawai Islands of Indonesia. At least 343 people were killed, and more are still missing. Survivors say they had no warning that a giant wall of water was headed their way: two buoys off the islands that were key to the tsunami warning system had been vandalized.

The 2004 Indian Ocean tsunami, which killed nearly a quarter of a million people, drove home the need to develop more and better warning systems. These systems can give people time to move to higher ground and get out of the way of the destructive water. But, as the most recent tsunami shows, we still have a long way to go.

That seems to be the message in an assessment of the U.S. tsunami warning system, released earlier this month by the National Research Council. "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," the scientists write.

Since 2004, the National Oceanic and Atmospheric Administration has improved their tsunami detection network. The main component of the system are the DART buoys, which are stationed in strategic locations in the Atlantic and Pacific Oceans and measure wave height. If a buoy measures an unusual wave, it transmits that information to shore.

The buoy stations are supposed to last about four years, but most don't make it past one, according to the report. They have become detached and drifted away. Sensors have failed. As many as 30 percent have been inoperable at any one time. As a result, the network has experience outages and compromised the ability of warning centers to issue tsunami warnings and forecasts.

To make matters worse, the two warning centers—based in Alaska and Hawaii—are not working together. They use different technology, have different responsibilities and are managed by separate offices. They can—and have—issued conflicting warning messages. In 2005, the Alaska office issued a warning to Oregon and California; Hawaii said it was unnecessary.

In addition, more efforts are needed to prepare the public for what is an incredibly rare, but deeply dangerous, event.

"Minimizing future losses to the nation from tsunamis requires persistent progress across the broad spectrum of efforts," the NRC report scientists write. "Sustained efforts...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."