Engineers and emergency planners from northern California to British Columbia say the massive undersea quake and tsunami that recently assaulted Japan gives clear warning about the danger that lurks just off the Pacific coast like a mad dog sleeping by the bed: A 630-mile-long geologic feature that was identified in 1984 is believed to be very similar to the one that broke with such violence off the coast of Japan in March. Evidence of violent breaks in the feature—called the Cascadia Subduction Zone, or CSZ—has been found in sediment layers left by prehistoric tsunami. On April 25, 1992, a 7.2-Mw
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.