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January 4, 2005

UCSC geophysicist creates computer simulation of Indian Ocean tsunami

By Tim Stephens

Soon after hearing news reports of the tsunami that devastated coastal regions throughout the Indian Ocean, research geophysicist Steven Ward, an expert on tsunami hazards, went to work on his computer.

UPDATE: Steven Ward was interviewed on campus this week for the television news program Dateline NBC. Although scheduling is subject to change, the program is expected to air on Friday, January 7, at 8 p.m. on local NBC stations.

Using sophisticated computational techniques to simulate the tsunami, Ward created an animated movie showing the tsunami waves spreading out through the Indian Ocean from the site of the powerful earthquake that triggered them.

The simulation, based on the physics of earthquakes and tsunamis, is preliminary because geologists have not yet fully characterized the earthquake, Ward said.

"The tsunami model depends on earthquake parameters, so as we learn more about the earthquake I will be able to refine it. But the essence of the phenomenon is captured in the animation," he said.

A magnitude 9.0 earthquake, the most powerful earthquake recorded in more than 40 years, struck underwater off the Indonesian island of Sumatra on December 26. The resulting tsunami caused devastation throughout South Asia, with the death toll now estimated at 150,000.

According to Ward, the speed of a tsunami depends on the depth of the water, with waves traveling as fast as 400 miles per hour in the deep ocean.

When they come ashore, they are typically moving at about 30 miles per hour, he said, adding that tsunami waves are very different from the waves one usually sees at the beach.

"It's like the ocean turns into a river and starts to flow onto the land. It's not a big crashing wave like in the Hollywood movies," Ward said.

Tsunamis can be generated not only by earthquakes, but also by undersea landslides and asteroid impacts. Ward has used computer simulations to study all of these potential hazards. In 2003, for example, he and asteroid expert Erik Asphaug, an associate professor of Earth sciences, published a paper describing the tsunami that could result from an asteroid that is on course for a close encounter with Earth in the year 2880 (see Currents story).

In the aftermath of the disaster in South Asia, he has been contacted by numerous media outlets, including the Washington Post, New York Daily News, Newsweek magazine, and local KION TV.


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