Massive tsunami destroyed deepest breakwater in the world
Breakwater in Iwate no match for tsunami which carried a momentum equal to that of 250 jumbo jets flying at 1,000 kph. -Yomiuri Shimbun, ANN
Japan - The massive tsunami that laid waste to the world's deepest breakwater on March 11 carried with it a momentum equal to that of 250 jumbo jets flying at 1,000 kph, according to calculations by a Waseda University ocean engineer.
The two-kilometer-long breakwater at the mouth of Kamaishi Bay, Iwate Prefecture, was completed in 2009 and recognized by Guinness World Records as the deepest breakwater in the world.
Before the earthquake and ensuing tsunami struck, the 20-meter-thick breakwater stretched out into the bay from the north and south edges of the bay, its top sticking out eight meters above the water's surface to protect the port.
The concrete wall's foundation measures 7 million cubic meters--seven times the size of Tokyo Dome--along the seabed at depths of up to 63 meters.
According to the Land, Infrastructure, Transport and Tourism Ministry, the breakwater was designed to resist a jolt and subsequent tsunami equivalent to those caused by the magnitude-8.5 1896 Meiji Sanriku Earthquake.
On Saturday afternoon, Tomoya Shibayama, professor of ocean engineering at Waseda University, viewed the Sanriku coast from a Yomiuri Shimbun jet.
From the air, he could see that an 800-meter section of the breakwater stretching from the north shore had been destroyed; the remnants of the breakwater were crumbling. The concrete blocks above the water's surface were facing all different directions.
The 750-meter-long, 40-meter-deep breakwater in Ofunato Port also was obliterated by the March 11 tsunami.
"With all its destructive force, the tsunami apparently slammed into parts of the breakwater that had already been damaged in the quake and toppled them," Shibayama said. "The wave's power was far beyond our predictions."
Many of the coastal levees--the final line of defense between the breakwater and the shore--also were swept away by the tsunami.
The 10-meter-high levee stretching along 2.5 kilometers of Miyako had been nicknamed "the Great Wall of China" by the locals, an apparent reference to their belief it would protect them.
The powerful tsunami, however, breached the levees and destroyed the city, transforming it into a muddy swamp.
In Yamadamachi, a 50-meter to 60-meter section of the levee collapsed under the power of the tsunami. The town is now covered in fishing boats, houses and gray mud.
Said the professor, "The whole country needs to revisit its disaster measures."
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