Distributed acoustic sensing(DAS)has become an important seismic observation technology due to its advantages of low cost,easy deployment and high-density spatial sampling.Particularly,it is increasingly combined with vertical seismic profiles(VSPs)for active seismic exploration or passive seismic monitoring.DAS sensors record seismic signals by detecting axial strain or strain rate generated by elastic wavefield.However,the current single component DAS-VSP data does not fully record the three-dimensional vector vibration signals of the underground elastic wavefield.Therefore,how to separate P or S waves from them for subsequent seismic imaging and parameter inversion is an important and challenging topic.Based on the theory of elastic wave propagation,this paper estimates the polarization directions at the receiver point using the dispersion relationship of P and S waves.The P/S wave separation of DAS-VSP data is achieved through polarization filtering that varies with frequency and spatial position.The results of synthetic data and real DAS-VSP data from the East China Sea indicate that this method can effectively separate P-wave and S-wave signals from single component DAS-VSP data,and provide essential data preconditioning for subsequent P-and S-wave velocity model building and PP/PS imaging.
维普
万方数据