Scientists defend tsunami warnings after nonevents

Oceanographers issued a bulletin telling Hawaii and other Pacific islands a killer wave was coming with terrifying force and that “urgent action should be taken to protect lives and property.”

But the tidal surge predicted after Chile’s earthquake for areas far from the epicenter never materialized.

By Sunday, authorities had lifted the warning after waves half the predicted size tickled Hawaii’s shores.

Scientists acknowledged they overstated the threat but defended their actions, saying they took the proper steps and learned the lessons of the 2004 Indonesian tsunami that killed thousands of people who didn’t get enough warning.

“Failure to warn is not an option for us,” said Dai Lin Wang, an oceanographer at the Pacific Tsunami Warning Center. “We cannot have a situation that we thought was no problem and then it’s devastating.”

Hundreds of thousands fled Saturday after scientists warned 53 nations and territories that a tsunami had been generated by the massive Chilean quake.

In the largest-scale evacuation in Hawaii in years, emergency sirens blared throughout the day, the Navy moved ships out of Pearl Harbor, and residents hoarded gasoline, food and water in anticipation of a major disaster.

Predictions of wave height in some areas were off by as much as 50 percent.
In Japan, where authorities ordered 400,000 people from coastal communities, the biggest wave was a 4-foot surge that hit Hokkaido.

Scientists worried the false alarm could lead to complacency among coastal residents — a disastrous possibility in the earthquake-prone Pacific Rim.

Another Chilean quake in 1960 created a tsunami that killed about 140 people in Japan, and devastated downtown Hilo.

Despite some of the panic, Hawaiian public officials called the evacuation “perfect” and said it was a good test case that proved the system worked.

The state had a long time to prepare: Hawaii is nearly 7,000 miles from where the quake hit, and the tsunami took 15 hours to arrive.

Predicting tsunamis is difficult, given the ocean’s vast size and volatile forces at work miles below the surface.

Scientists use an earthquake’s magnitude and location as the basis for their predictions and then refine it constantly with data from more than 30 deep-water sensors stationed across the Pacific as the shock wave sweeps across the ocean floor.

The sensors, located at 15,000 to 20,000 feet beneath the surface, measure the weight of the water and beam it to buoys floating on the surface. Scientists then use the data to calculate the tsunami’s wave height in the open ocean as it progresses toward shallower waters.

Because complete data doesn’t exist for every coastal area, scientists must play it safe in their wave predictions, Wang said.

Residents and tourists in Hawaii said they weren’t bothered by the evacuation and supported the scientists’ actions.