Tsunami Warning System Could Have Saved Lives

By Dr. Robert Thorson

The death toll from the Sumatran tsunami will probably exceed 50,000. Regrettably, most of those drowned at sea died needlessly, either because they were not adequately warned or because they couldn’t interpret the sea’s strange behavior. Ignorance of earthly matters always takes its toll.

A sophisticated tsunami warning system operates 24-7 around the Pacific Rim. There, 25 nations have formed a coalition led by the United Nations to share the cost of gathering data on the events that generate tsunamis (earthquakes, volcanic eruptions, submarine landslides, asteroid impacts) and the waves that are propelled outward.

When a generating event occurs, all nations share the benefit of being alerted to giant waves speeding in their direction. This system was created in 1965, following the destructive tsunami caused by the 1964 Alaskan earthquake, which killed 10 people as far away as Crescent City, Calif.

An even larger tsunami was caused by the 1960 Chilean earthquake near Valdivia, which created waves that killed 200 as far away as Japan.

I have witnessed the lasting tsunami damage near the epicenters in Alaska and Chile. I also spent time on outer beaches of the tsunami-prone Oregon coast while attending a conference on Pacific Coast geologic hazards. In Oregon, I saw exemplary civil preparedness against the tsunami hazard: antennas to receive broadcasts; sirens mounted at regular intervals; prominent warning signs with instructions; pamphlets to read at your leisure; clearly marked evacuation routes; and fortified buildings for emergency refuge. Reflecting on my visit to Oregon while watching the devastation now bordering the Indian Ocean made me wonder how many lives could have been saved from the Sumatran event had the civil preparedness been equal to the Oregon standard.

The day on which a tsunami will occur cannot yet be predicted, and there remains little hope for those closest to the source to be notified in time. But once the wave is moving across the open ocean, predicting its arrival time is not unlike predicting when a prairie freight train moving at a constant speed will arrive.

A Pacific-rim-style warning in Sri Lanka — where the death toll was highest — would have given its residents more than an hour to move out of harm’s way. In fact, the National Oceanographic and Atmospheric Administration, using its own data, put out an all- points danger bulletin 100 minutes before the first waves struck this devastated island nation, but the information seems to have gone nowhere.

In fact, there are four levels of warning, all of which seem to have been generally ignored. First is the geologic setting; geologists know that any nation facing the sea toward Sumatra is at risk. Second would have been a warning-preparedness system similar to that in the Pacific. Third, local communities can monitor buoys or tide gages for the anomalous fall or rise in local sea level that accompanies an approaching giant wave. Finally, the most urgent sign of a destructive tsunami is rapid withdrawal of water away from the land — as if the tide were going out faster and lower than expected. This phenomenon was reported for the recent Sumatran event.

Tsunamis, a Japanese word for harbor waves, are caused by displacements of the sea floor that have nothing to do with tides or wind. Imagine a sheet of plywood hinged to the bottom of a swimming pool somewhere near the edge. Imagine lifting the sheet rapidly and effortlessly with tectonic strength. The bulge of water lifted will immediately migrate outward in all directions at a constant rate, causing negligible disturbance near the middle of the pool, but sloshing every edge at a predictable time. In the real world, the near-shore bathymetry and form of the coast influence the severity of the slosh and degree of destruction. In a nutshell, the arrival time of the hazard is predictable; its severity less so.

I draw two lessons from all this. First, life isn’t fair. Why should the Pacific Ocean have it so good, the Indian Ocean so bad? Second, every person on the planet can help mitigate his or her own exposure to the tsunami hazard simply by learning a little bit more about how the Earth actually works.