[scarab92]

The concrete is supported by formwork and props until it cures, which appear to have been removed on all floors, suggesting that the concrete structure was now complete and the building is about as strong as it ever will be.

The collapse must have been due to a design or construction mistake.

[defrost]

There are a number of post concrete cured enhancements to buildings that improve earthquake resistance that may not yet have been added (if planned) .. antisway damping, additional bracing and or bridge like cabling, etc.