**Jie Fang, Guofeng Liu \* and Yu Liu**

School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China; fangjie@cugb.edu.cn (J.F.); 3010200013@cugb.edu.cn (Y.L.)

**\*** Correspondence: liugf@cugb.edu.cn

**Abstract:** Passive surface wave imaging based on noise cross-correlation has been a research hotspot in recent years. However, because randomness of noise is difficult to achieve in reality, prominent noise sources will inevitably affect the dispersion measurement. Additionally, in order to recover high-fidelity surface waves, the time series input during cross-correlation calculation is usually very long, which greatly limits the efficiency of passive surface wave imaging. With an automatic noise or signal removal algorithm based on synchrosqueezed continuous wavelet transform (SS-CWT), these problems can be alleviated. We applied this method to 1-h passive datasets acquired in Sichuan province, China; separated the prominent noise events in the raw field data, and enhanced the cross-correlation reconstructed surface waves, effectively improving the accuracy of the dispersion measurement. Then, using the conventional surface wave inversion method, the shear wave velocity profile of the underground structure in this area was obtained.

**Keywords:** passive seismic; noise separation; surface wave; dispersion curve
