This reinforced concrete-deck highway bridge across Twentymile River near Turnagain Arm of Cook Inlet fell into the river during the earthquake; the adjacent steel railroad bridge survived with only minor damage. Both bridges were founded on thick deposits of soft alluvium and tidal flat mud, and were subjected to severe seismic vibration. During the earthquake some of the concrete deck sections hit the underlying wood piling with sufficient force to drive the bare ends of the wood piles through the concrete deck.

Image Credit: U.S. Geological Survey