The Second-Order Synchrosqueezing Continuous Wavelet Transform and Its Application in the High-Speed-Train Induced Seismic Signal

Thousands of high-speed trains (HSTs) run on over 30000-km high-speed railway every day in China. These running trains not only cause vibrations but also stimulate all kinds of seismic waves. The receiver seismic signal’s spectrum has one special equal-interval, multinarrowband feature. Some commonly used time-frequency (TF) analyzing methods, such as the short-time Fourier transform, continuous wavelet transform, and the Stockwell transform, can capture a signal’s TF features and reconstruct signal without loss. However, their TF resolution is limited by the uncertainty principle. In this letter, we apply the second-order synchrosqueezing continuous wavelet transform (SSCWT), which is one improved SSCWT, to the HST induced seismic signal and capture its TF spectrum features. The synthetic data example and real data example have proved the second-order SSCWT can provide a more concentrated TF spectrum than the commonly used SSCWT.