Tokyo "downtown" doesn't have most of its transit above ground. There are only ~3 lines above ground in the center of Tokyo. The Yamanote, the Chou, and the Sob

Tokyo "downtown" doesn't have most of its transit above ground. There are only ~3 lines above ground in the center of Tokyo. The Yamanote, the Chou, and the Sobu lines. Compared to 14 below ground. And, they've built plenty of new lines underground. The Oedo line which opened in 2003 is entirely underground. The Fukutoshinsen line which opened in 2013 is entirely underground. The Tsukuba line, 2005, is underground at least downtown. It's often said the being in the subway in Tokyo is one of the safest places to be in an earthquake. It might be scary but things are less likely to fall from 10 to 20 stories on your head like they are in outdoors in Tokyo. http://blogdowntown.com/2012/08/6959-metro-tunnels-are-one-of-the-safest-places http://blogdowntown.com/2012/08/6959-metro-tunnels-are-one-o... On top of that for a place like SF subways don't have to be deep. It's not like there's 100 meters of earth above the subway. There's the street, under which there's the line. The only thing above your head is effectively a bridge construction except unlike a bridge it's got continuous support instead of a leg every 50 meters.