The identification of mode shapes is an important but challenging task of vibration based system identification procedures. We propose a simple and robust procedure for extracting mode shape information from the vibration signatures of structures with particular reference to the earthquake excitation cases. A wavelet based synchrosqueezed transform technique is used to decompose the measured vibration response into individual modal response components. The modal frequencies and mode shapes are obtained from the analysis of these isolated modal components. The proposed scheme is validated by considering the response of UCLA Factor Building for a suite of three different ground motions.