Synchrosqueezing Transform-Based Frequency Shifting Detection for Earthquake-Damaged Structures

Analysis based on time-frequency representations provides meaningful interpretations for seismic signals. An application of the synchrosqueezing transform (SST) based on continuous wavelet transform for the detection of frequency shifting of earthquake-damaged structures is introduced in this letter. The analysis of real-time seismic records of the damaged structures is performed with Wigner-Ville distribution, S-transform, and hybrid transform, which is known as Gabor-Wigner transform. The detection of frequency shifting with SST for synthetic and seismic signals outperforms the other time-frequency distributions tested. SST improves the frequency localization by reducing smearing around frequency components and it also yields good time localization, which is comparable with S-transform. The small variation in the natural frequency of earthquake-damaged structures is detected through SST-based analysis. Hence, we show that SST improves the readability and interpretation of the time-frequency representation of frequency shifting in damaged buildings caused by large earthquakes.