To explain the strong ground motion of an earthquake, a time history of that earthquake is used most widely. The recorded seismic signals display non-stationary and non-linear characteristics and express a time evolving frequency composition. The proper analysis of ground motion signal provide the useful information for infrastructure development in seismically active area, for prediction of earthquakes and to quantify the damage from the recorded motions. The temporal variation of a signal like earthquake ground motion alone is not adequate to get the physical process involved. Therefore, alternate representations have been evolved for better understanding of the characteristics of signal. Considering the limitation of Fourier Transform of not revealing the temporal information of change in frequency contents occurs, joint time–frequency representations is presented as a demonstration of time and frequency both. A popular method to get the preferred time–frequency information available in a non-stationary signal, is Continuous Wavelet Transform (CWT). However, this method suffers from uncertainty principle and have limitation in terms of resolution. The results through Continuous Wavelet Transform of non-stationary, non-linear signal may be improved by computing the instantaneous frequency of wavelet coefficient, that is followed by reassignment step. The derivation of CWT empowered by the reassignment step gives the Synchrosqueezing Transform. In this paper, Synchrosqueezing Transform (SST)-based technique is adopted for seismic signal’s joint time–frequency representation. This paper evaluated the effectiveness of SST by implementing it on a non-stationary and non-linear synthetic signal as well as real-time ground motion signal of Uttarkashi earthquake (Oct. 1991). The resolution improved to a great extent, better time and frequency localization are observed in results of Synchrosqueezing Transform-based method.