Seismic performance is an execution of a building structure's ability to sustain its due functions, such as safety and serviceability, "at" and "after" a particular earthquake. A structure is, normally, considered "safe" if it does not endanger the lives and wellbeing of those in or around it by partially or completely collapsing. A structure may be considered "serviceable" if it is able to fulfill its operational functions for which it was designed.