“…The causes may also be related to non-linear responses of the buildings. For example, transient variations are observed during seismic excitation due to the non-linear response of the soil-structure boundary (e.g., Jennings and Kuroiwa, 1968;Crouse and Jennings, 1975;Todorovska andTrifunac, 2008, Todorovska, 2009) or to the closing/opening process of pre-existing cracks within the elements of the reinforced concrete buildings (e.g., Luco et al, 1987;Meli et al, 1998;Clinton et al, 2006;. Permanent variations may also appear due to structural damage due to strong seismic motion (e.g., Safak and Celebi, 1991;Celebi et al, 1993;Dunand et al, 2006;Clinton et al, 2006).…”