Aftershock records have a considerable effect on the results of collapse assessments conducted on buildings. Thus, they should be selected cautiously. As the number of recorded aftershocks is not sufficient, mainshock records are often utilized instead. In order to increase the correlation between the aftershock time history and the seismic response of a structure, this research intends to investigate several Intensity Measures (IMs). For this study, three RC frames were considered. Forty-four far-field records from FEMAP-695 were selected as main and aftershock. Each building analysis was conducted under 44 mainshock–aftershock chains. According to the results, use of the summation of the first mode spectral acceleration value of aftershocks as the second part of a vector IM can lead to the sufficiency of the IM.
