Overview:On March 11, 2011, a huge earthquake occurred off Japan's Tohoku coast. Skyscrapers 400 kilometers away in Tokyo's Shinjuku district continued swaying for 13 minutes. And 770 kilometers away in Osaka, tall buildings swayed for more than 10 minutes. This swaying was caused by "long-period seismic waves", which can travel long distances at frequencies that resonate with high-rise buildings in particular. In this episode, we'll look at some of the steps being taken to address this problem, including heavy weights installed atop high-rises.