July 26, 2005

Reaching Safe Ground

Some researchers are combining geophysical data with findings from social science in an effort to save more lives during a natural disaster.

By David Wolman

If a major earthquake happened in the Cascadia Subduction Zone, a tectonic plate margin similar to the one where the devastating earthquake and tsunami occurred last December in the Indian Ocean, people in low-lying towns along the Pacific Northwest coast would have an estimated 30 minutes to evacuate.

Given that dire, but realistic scenario, would it be more effective to broadcast evacuation instructions to residents of, say, Seattle via a fleet of cars that sound an alarm, announcements over the radio, or reverse-911 calling with cell-phone paging?

As geoscientists and engineers throughout the world study the physics of "killer" waves and how to design structures that might withstand them, other researchers are focusing on an even slipperier area: human behavior.

"Social science has to play a major role in hazard preparedness," says George Crawford, earthquake program manager for the state of Washington's emergency management division.

Leading this effort at incorporating human factors into the field of disaster mitigation is Toshitaka Katada, a professor of social engineering at Gunma University in Japan. About six years ago, he realized that the flood modeling programs he was working on might also be valuable for reducing the losses from tsunamis. Today, in association with Harry Yeh, a professor of ocean engineering at Oregon State University (OSU), Katada is developing a model called the Tsunami Scenario Simulation.

At its core, this simulator applies classic physical factors involved in a tsunami: hydrodynamics, wave propagation, inundation, impact, and destruction and debris within a geographic area. 

"We have studied tsunamis theoretically and experimentally for a long time," says another researcher in the field, civil and environmental engineer Tomoyuki Takahashi of Akita University. "We know the characteristics and have the governing equations."

This complex physical understanding, in part, is due to investigations at places like OSU's wave laboratory, where researchers run waves through a giant, concrete channel large enough for someone to surf in (see Sources in Notebook). Scientists also carry out mock seismic events in another, equally huge tank that sends waves hurtling toward miniaturized coastlines.

The Tsunami Scenario Simulation takes this traditional physical-world model -- and then overlays it with social phenomena that simulate the movement of both information and people through time and space. Modeling these social dynamics allows researchers to test the efficacy of different types of warning transmissions, different evacuation routes, the role of word-of-mouth, demographic details about age and culture, and local information such as the location of schools and nursing homes.

In one such simulation, a series of blue waves sweep toward land from the side of the screen, while blinking lines indicate evacuation routes and color-coded symbols identify people who have drowned, major debris hazards, traffic bottlenecks, and more.