A tsunami that struck west of Sumatra last week brought with it a torrent of questions and speculation about why villagers weren’t warned in advance of the ten-foot waves that buffeted the Mentawai Islands.

Local officials claimed early warning systems had been vandalized, while alert agencies said the systems worked fine and warnings were issued accordingly. Scientists reminded the public no system is fail-safe, especially when a quake strikes close to shore like it did in this case.

While most of these responses are valid (the vandalism may or may not have happened), they don’t address the fact that nearly 450 people are dead, ten villages are decimated, and those at risk have one less reason to put their trust in tsunami warning systems.

In Mentawai, scientists estimated waves were striking the remote beaches about five minutes after the quake and less than 15 seconds after a warning had been sent to regional agencies to sound the alert, according a Nature blog.

“Earthquake and sea-level monitoring systems are in place, but what has proven more difficult is how to get warnings out to remote areas in time,” UN Disaster Risk Specialist Tiziana Bonapace told the BBC. “This remains the weakest link in the system, and unfortunately the tsunami hit one of the farthest outlying islands. Further exacerbating the situation is that buoys do malfunction, and many countries have been experiencing difficulties in this regard.”

Even when the equipment is in good working order, it can take valuable time to transmit and analyze the data. Nearly a year ago, 150 people died in Samoa due to a similar near-shore quake. In that incident, it took 18 minutes to issue a warning—about the same time it took the waves to reach the shore, according to the Christian Science Monitor.

While in hindsight the lapse might seem avoidable, scientists have to carefully weigh caution with accuracy, James Goff, director of the Australian Tsunami Research Centre, told the Monitor.

“There would be a lot of false alarms, then when a real tsunami happened, people would ignore the warning and get killed,” he said.

A good example of a tsunami false alarm came in late February, when nearly 150,000 people were evacuated from coastal areas in Hawaii and warnings were issued as far away as California. Although data from Pacific Tsunami Warning System buoys suggested an earthquake off the coast of Chile would create monster waves, they somehow dissipated, maxing at about three feet by the time they reached the shore.

“Forecasting tsunamis is a relatively new science. We learn a lot every time we have an event like this,” National Weather Service Tsunami Program Coordinator Jenifer Rhoades told the Washington Post at the time. “We dodged a bullet this time, but since tsunami science is not exact, we erred on the side of caution.”

So what’s the answer, considering the limits of technology and the delicate art of maintaining public trust? Shoring up the science with a combination of public awareness and clear communication, according to John Orcutt, chair of a recently released National Academies report on tsunami warnings and preparedness.

“For a tsunami warning system to be effective, it must operate flawlessly, and emergency officials must coordinate seamlessly and communicate clearly,” he stated in a release. "However, 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. Education and preparation are necessary to ensure that people know how to recognize natural cues—such as earthquake tremors or receding of the water line—and take appropriate action, even if they do not receive an official warning.”