LONDON (AlertNet) – Researchers have used eyewitness videos showing the giant waves that devastated Japan’s coast during the 2011 tsunami to provide insight into how waves behave when they hit land, which could provide vital information when it comes to designing buildings to withstand another disaster and planning escape routes, New Scientist reported.
They say automated camera systems should be routinely deployed to warn people of disasters, the magazine said in its March edition.
Existing computer stimulations can determine how the waves behave when out at sea and as they approach the coastline. But it is almost impossible to forecast which direction the water will go and how big the waves will be once they hit the land.
As Japan’s tsunami showed, the true magnitude of the disaster triggered by a 9.0 magnitude earthquake only became clear once the waves hit the shore, sweeping thousands to their deaths.
In the fishing port of Kesennuma, which was on the front line of the March 11, 2011 tsunami, eyewitnesses who had fled to the rooftops of two tall buildings recorded the devastation with handheld camcorders.
By carefully analysing the footage, Costas Synolakis of the University of Southern California in Los Angeles and Hermann Fritz of the Georgia Institute of Technology in Savannah were able to reconstruct the event minute by minute, New Scientist said.
Synolakis and Fritz recorded both water heights and flow rates as Kesennuma was engulfed. Using laser rangefinding, they then synchronised cameras’ field of view with real-world coordinates to eventually calculate the rates of flow.
The waves rose to a height of 9 metres in the city, and currents reached a peak of 11 metres per second - almost 40 kilometres per hour - as the water rushed back out to sea.
Even though knowing the speed of a tsunami wave may not be much helpful for communities located right at the coast, it may help design a warning system for areas further away, giving people critical minutes to escape and also plan the best evacuation routes.
Cameras installed in harbours would trigger specific warnings for areas that are further away if a major wave was coming.
And, as Synolakis argues, already existing security cameras could also be used to create a live-saving monitoring system.
The earthquake and tsunami killed about 16,000 people and triggered the world’s worst nuclear crisis since Chernobyl. About 326,000 people are still homeless a year after the disaster.
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