The Tohoku tsunami was Japan’s deadliest in more than 100 years. Despite an extraordinary level of preparedness by the Japanese, the tsunami caused more than 90 percent of the almost 20,000 fatalities last March.
Hermann Fritz, Georgia Tech associate professor of civil and environmental engineering, and his research team are studying the impact of the tsunami on the Sanriku coast. Using eyewitness video and terrestrial laser scanners from atop the highest buildings that survived the tsunami, Fritz has mapped the tsunami’s height, velocity and flood zone to learn more about the flow of the devastating currents.
What we can learn from the hydrograph is confirmation that the water goes out first, drawing down to more than negative 3 meters on the landward side of the trench, which can make vessels hit ground inside harbors. During the subsequent arrival of the main tsunami wave, the water rushing back in changed the water level by 40 feet, engulfing the entire city in 12 minutes.
Understanding tsunami velocity will help prepare for future disasters—whether its designing buildings high enough to serve as vertical evacuation points, or sea walls and breakwaters strong enough to control the flow of water.
The ultimate goal is to save lives. In order to do so, we have to have a better understanding of what worked and didn’t work. This is the first time we’ve been able to look at the structural infrastructure designed to protect coastal towns from tsunamis and examine why it didn’t work. There’s a lot to learn in terms of surviving tsunamis and protecting, evacuating and ultimately saving lives.
For more on the anniversary of the Japan disaster, visit www.gatech.edu/experts/japan-anniversary.
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