Tsunami Prediction: What Can and Can’t Be Done to Save Lives
This aerial image shows tsunami tidal waves moving upstream in the Naka River in Ibaraki prefecture on March 11; STR/AFP/Getty Images
As horrific as the March 11 earthquake and tsunami were in Japan, they were exciting events for geologists and oceanographers around the world. While not rare, big tsunamis are infrequent enough that scientists are eager to jump on them for study.
“When I heard there was a tsunami in Japan, I was not able to sleep that entire night,” said Bruce Jaffe, a geologist with the U.S. Geological Survey in Santa Cruz, Calif. “I felt it was my duty as a scientist to track what was going on and to let people know as much as possible what I thought the risks were.”
As it turns out, the risks are pretty high, depending on where you hang out. Obviously, in Japan, near Sendai, the danger was upon people before they had much chance to get away. A large 9.0 earthquake just offshore triggered the waves that smashed into the coastline, causing untold damage and costing perhaps 20,000 lives. The enormously powerful tsunami that followed ran onto the land and — according to Eddie Bernard, a scientist at the National Oceanic and Atmospheric Administration — climbed 130 feet above sea level, even higher than the Indonesia quake in 2004.
But tsunamis spread in all directions. Nine hours after the Japan quake, some waves reached the West Coast of the United States. Those waves were small – two to three feet – but they carried huge amounts of energy. So when they entered the harbors in Santa Cruz and Crescent City, Calif. — 6,000 miles from Japan — they smashed into boats and docks, causing millions of dollars damage. One man was killed, trying to take pictures of the waves.
Much of the Pacific Coast and most of Hawaii were spared, just as scientists knew they would be. The shape of the bottom of the ocean — bathymetry — plus the power of the quake told them that the tsunami would follow a predetermined path, and that the harbors in Santa Cruz and Crescent City, partly because of their shape, would get hit harder than the nearby coastline. In Hawaii, a warning went out on Maui, and people evacuated – most likely saving lives.
While scientists can trace the path of the wave energy, and predict when and where the waves will hit, what they can’t do is predict the earthquake that triggers the tsunami. Bernard has been studying tsunamis for 40 years, probably longer than anyone, as a geologist with NOAA’s Tsunami Research Center in Seattle. He told me that the source of the earthquake that starts a tsunami will probably remain a mystery.
While earthquake prediction has yet to be perfected, tsunami prediction is very possible once the earthquake has occurred, and in fact that’s what Bernard and his colleagues do. They have placed sophisticated buoys in the ocean near earthquake zones that precisely read the water pressure on the ocean floor to determine if a tsunami is present. Then they relay that information to the buoy on the surface, which sends it via satellite to tsunami-warning centers run by the weather service. I spoke with Ted Buehner, the warning coordination meteorologist with the National Weather Service in Seattle, who explained how they spread the word:
With all the planning and coordination, however, if an earthquake triggers a large tsunami close to shore, there will be very little warning time. That’s what happened in Japan; people had almost no time to escape. And that’s what residents of the Pacific Northwest — from Vancouver Island in Canada, south to Washington, Oregon and Northern California — fear.
A geological feature of the earth’s surface, called the Cascadia Subduction Zone, could rupture, as it did in the year 1700, and create a huge tsunami that could hit the shore within minutes. That’s a scary scenario that could bring massive destruction, despite the network of buoys, warning systems, and escape routes that the tsunami planners have devised.