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 wavesweeps 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 pinpoint where the surge is and when it will make landfall.
Coastal inundation models based on topographic mapping add another layer of analysis, helping scientists make assumptions about how the surge will behave in shallower waters and how it might affect shoreline communities.
“There are all sorts of assumptions that we make in trying to figure out how big the waves are going to be. If we can avoid some of those assumptions, maybe we can do a better job,” said Fryer.
“If this event happened tomorrow, even with this knowledge, we would be forced to do the exact same thing.”
Those models could be more accurate if scientists had more deep-water sensors and could build coastal inundation models for vast parts of the Pacific Rim where the topography hasn’t yet been well-surveyed, Wang said.
Because complete data doesn’t exist for every coastal area, scientists must play it safe in their wave predictions, he said.
“Even for Hawaii, we only have a forecast for less than 10 locations, we don’t have inundation models for every coastal point in Hawaii and it’s the same story for the U.S. mainland,” Wang said. “We’ve got to be a little conservative. One point doesn’t tell you that’s going to be the maximum everywhere else.”
In areas were inundation models exist, scientists’ predictions were close to accurate, Wang said.
Residents and tourists alike in Hawaii said they weren’t bothered by the evacuation and supported the scientists’ actions—even though the waves never showed up.
But Okamoto said his family understands the tsunami threat better than most because some of his relatives lived through the tidal surge in 1960. They remember how the water was sucked down the beach moments before the wave hit.
“My uncle was on the top floor when all the water washed away and all the kids ran out to grab the fish and before they could get back, the wave came. He was way up top, he saw all his friends get washed away and none of them were found, ever,” Okamoto said, as he sat with his father in a hotel lobby. “They did the right thing.”
I’m with Mr. Okamoto.