The paper presents the revised formulation of a signal processing methodology aimed at identifying the dynamics of buildings hit by earthquakes. The methodology is based on the Gabor joint time-frequency representation and allows to identify an evolutionary modal model whose time changes are used to evaluate the damage presence and severity. Dynamic tests are performed in advance to provide reference values and their confidence ranges used for the assessment of the results. The methodology has been extensively applied to the buildings belonging to the Italian national network of seismic structural monitoring. A sample application referred to a representative reinforced concrete buildings is shown.