Many homes with slab foundations did not have detailed foundation assessments completed by EQC, and often no floor levels were taken. For many homes the foundation inspection stopped at the garage slab.
However, since many foundations built prior to the Canterbury Earthquake Sequences (CES) do not have mesh in the slab, many have experienced slab cracking damage, and that damage has been missed. In addition, foundations built prior to the CES in Canterbury used river rounds in the subbase, and earthquakes can cause movement to the subbase according to Tonkin and Taylor.
If you have wall linings that are still showing signs of movement, perhaps unusual humps or hogging in the floor, doors that do not shut correctly, they can all be indications of missed foundation earthquake damage.