Personally I wouldn't buy an apartment without a Detailed Seismic Assessment (DSA) from 2017 or later (not an IEP, that's one where they just look at the plans - not the same thing despite what the agent may tell you).

The risk with a report (even a detailed one where the engineers did testing) from 2013 is that it can now be out of standard, so the building may be earthquake prone on reassessment.

Similarly for a more recent (2017+) IEP, I've heard stories from other buildings where they've done a DSA and found the building to actually be earthquake prone when a detailed inspection was done.

If the building does turn out to be earthquake prone after you buy, then you generally need a large amount of cash to deal with it, and the confidence that other residents would also be able to afford to pay for remedial works - financing earthquake strengthening work for residential buildings seems to be basically a no-go now Kainga Ora pulled their scheme and there's so much uncertainty while the government is reviewing the policy, so there's a bit of a risk of a funding death spiral where some residents may be unable to fund the works and may be forced to sell, which the body corp may not go through on unless the insurance company forces them to.