Earthquake resistance to Eurocode 8

My points ,
- EN 1998 has 6 parts and 1998 Part 1: General rules, seismic actions and rules for buildings ..
- There is a near collapse (NC) limit state concept . It is used as a conservative approximation of structural collapse and in Eurocode 8, Part 3, the NC limit state is defined as follows:
LS of Near Collapse (NC). The structure is heavily damaged, with low residual lateral
strength and stiffness, although vertical elements are still capable of sustaining vertical
loads. Most non-structural components have collapsed. Large permanent drifts are
present. The structure is near collapse and would probably not survive another
earthquake, even of moderate intensity.
- NC limit state is typically based on a mean return period of 2475 years (2% probability of being exceeded in 50 years).

The standards are minimum requirements IMO , provide legal shield for the designer. Moreover , the client / owner has the right to ask more to design with more stringent requirements. Sometimes the owner may ask for designing with higher importance factor .

Suggest you to look to the following doc. (Performance Based Design , performance requirements )