Tunnel Seismic P and S Waves Separation Method Based on Instantaneous Polarization Parameters

In tunnel seismic forward-prospecting, the coupling of P and S waves often leads to significant crosstalk in inversion or migration imaging, complicating the interpretation of the geological conditions ahead of the tunnel face. F-K and $\tau -p$ filtering methods are currently widely used for P and S waves separation. However, their effectiveness is often limited by the accuracy of wave velocity estimation, leading to less than satisfactory separation results. This letter introduces an innovative method for separating P and S waves in tunnel seismic data, leveraging instantaneous polarization parameters in the time–frequency domain. By integrating the high-resolution time–frequency analysis of the synchrosqueezed wavelet transform with the precise localization capabilities of the polarization principal axis parameters, our approach achieves more accurate calculations of the azimuthal polarization parameters in seismic data. This enables the design of a novel filter for separating P and S waves based on azimuthal polarization parameters, with separation thresholds rigorously calibrated through extensive numerical simulations. The proposed method demonstrates the superior performance on both synthetic and field data, yielding much clearer P-wave and S-wave separation than traditional F-K filtering. This highlights its potential for advancing the practical application of tunnel seismic forward-prospecting.