are one or two stories high. they tune into a different motion of the earthquakes. if this was a earthquake of some duration such as 30, 40 seconds, i don t know, maybe a minute, bridges would certainly be affected. bridges generally cross rivers with weak soils. that would amplify the ground motions, as well. that fully explains why we are seeing these dramatic pictures. it looks to be one tall spire, a tower of concrete supporting this bridge standing alone literally. everything standing between one tower and the next has fallen into this river/ravine area. take what you know about this and apply that to the cities that are more heavily populated. we saw some highways that seem to have collapsed upon themselves, certainly not at this altitude.