safety evaluation of buildings by aftershocks

Earthquakes can affect the performance of civil structures significantly. iran is located on alpine-caucasian- himalayan belt, so earthquakes are major threats for the structural stability and safety in this country. immediately after a seismic event, safety evaluation of buildings in the earthquake stricken area is essential for decision-making. in other words, post-earthquake structural safety assessment is a key to determine whether an earthquake-damaged structure is safe to re-occupy or not. current assessment practices rely mostly on visual inspections conducted by experts and assign green, yellow or red tags on buildings that are apparently safe, restricted for use and unsafe to occupy, respectively. atc- 20 is one of the most common guideline for this practice; it has a three-level evaluation methodology: rapid evaluation(emphasis is on the exterior of the building), detailed evaluation (requires a thorough examination of the interior and exterior of the building), and engineering evaluation (when visual inspections are not sufficient to determine damage to the building).