We are actually pretty near earthquake country, St. Louis is almost on top of it. The New Madrid fault sparked 2 huge quakes in the 1800's when the area was relatively unpopulated. They altered the path of the Mississippi river. People here are going to get the shock of their lives one day. Nothing as far as I know is built to Earthquake code.
Yeah, there’s a lot of places that are known earthquake areas (like Manhattan Island) that are not anywhere built to the standards of construction that would withstand a likely earthquake. Especially in the New Madrid Zone where buildings built after the last Madrid quake are made out of unreinforced brick.
If or rather when there’s another significant quake there, it won’t be a rude surprise, it’ll be a nightmare for the thousands who will find themselves in brick rubble.
Some things are, but most doesn't appear to be up to a real shaker.
If you look at the bridges and overpasses along I-40 in the vicinity of Memphis, TN, you'll see cable restraints that have been installed between the bridge abutments and the spanning girders to reduce the chance that the bridges will shake apart and collapse during a major quake. Other than that, though, there aren't many visible signs I've seen of any earthquake code being followed like what you see in So. Cal.....