This study presents a novel method to quantify the damage gradually developed during an earthquake. A damage-sensitive parameter is introduced based on the normalized wavelet decomposition of representative vibration signals during an earthquake. Story acceleration and roof displacement are representative vibration signals. Furthermore, the study examines the effects of the number of floors, PGA, PGA/PGV, and Impulsivity Index on the robustness of the proposed method. Four seismic ground motions are applied to the 6 and 8-story moment resisting frames. The results of the analyses show that the proposed method quantifies the extent of the damage using story acceleration. However, a damage-sensitive parameter based on roof displacement cannot accurately quantify the damage. The suggested damage-sensitive parameter depends more on earthquake properties than on structure characteristics. Among PGA, PGA/PGV, and Impulsivity Index, the damage-sensitive parameter is related to the Impulsivity Index of the ground motions
