Basic EQ Eng. Principles
Engineering profession has long taken position that because earthquakes are rare events, structural damage is acceptable in engineered buildings, provided that collapse is prevented.
This has been achieved by ensuring that structural components in the systems designed to resist the seismic loads are able to sustain their strength while undergoing large inelastic deformations.
This ability to resist large inelastic displacements in a stable manner has been termed "ductility".