From pics I have seen the smaller buildings and shanties look like they went through a grinder. Entire slum neighborhoods looked like a debris pile from a demolition project.

Block and concrete buildings disintigrated for lack of reinforcing and poor quality of the concrete.

There is no reinforcing steel for two reasons #1 cost and #2 concrete made with beach sand is salty and corodes the steel. coroding steel expands cracking the concrete. solutions to this problem are expensive (epoxy coated steel or non-ferris reinforcing).