Tsunami Science: Reducing the Risk

From Math to Maps

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For the model to predict where and when the wave would hit, and how hard, Titov desperately needed bathymetric data for coastal regions around the Indian Ocean. This information, regrettably, was both scarce and impossible to access in time. When combined with political hurdles and an infrastructure not suited to handle tsunami warning in the Indian Ocean basin, NOAA’s efforts were unable to help avert some of the disaster’s more than 283,000 deaths.

NOAA computer modeler Vasily Titov and the model he made within hours of the Indian Ocean tsunami.

Jason Lelchuk for AMNH

Toward the Future

Still, Titov’s Sumatra model is incredibly useful for mitigating the effects of future tsunamis. Researchers are now comparing its predictions to the wave’s real-life effects on coastlines around the world. “Every tsunami leaves traces on the coast,” says Titov. “So we go to the hardest-hit coasts and measure how high the wave came up the shore, or on trees. That gives us the amplitude data for the tsunami at different coasts.”

Worldwide data on the tsunami is still being collected months after the event. Some of it has been surprising, and illuminating. For example, the tsunami took 30 to 32 hours to reach the most distant coastlines, such as those in Halifax, Nova Scotia, 24,000 km from Sumatra. Curiously, some wide-ranging spots like Halifax and Lima, Peru, recorded waves several times larger than those that hit the Cocos Islands in Australia, only 1,000 km from the source. “Now we realize how a tsunami can import energy into different oceans,” says Titov. It turns out that the energy can be channeled by mid-ocean ridges: long, underwater mountain ranges formed by magma rising up in between plate boundaries. “The mid-Atlantic ridge provided the pathway for the tsunami into the Atlantic,” he explains.

Overall, Titov’s Sumatra computer model closely matches the real event. That means the calculations can be applied to models modified for use in places like the Pacific Northwest, which has a coastal fault line of the same type and length, and with similar bathymetry, as Sumatra. A magnitude 9 earthquake there could produce a tsunami that could affect coasts worldwide. Since local communities would be hit hardest, however, Titov is now working to test dozens of scenarios with his models, trying different combinations of earthquake magnitudes, locations, and local bathymetries in northern California, Oregon, Washington, and British Columbia. If an earthquake occurs at any fault in the Pacific basin, emergency managers could draw from this stockpile of scenarios to predict wave characteristics and time of strike at a particular coastline.

A prototype system for such model forecasting is already in place, and is now being tested by NOAA and by tsunami warning centers responsible for events in the Pacific, Atlantic, and Caribbean. (As for the Indian Ocean, a warning system is still being set up, negotiated, and organized both technically and politically, says Titov.) The hopes are that within a year, NOAA’s system will be able to generate model forecasts in a matter of minutes. “We definitely don't want the Sumatra case to repeat itself,” he says. “We’re hoping to get our system in good enough shape so that the next big tsunami will not catch us by surprise.”