PS Interferometric Cross Correlation Imaging Condition for Seismic Source in Elastic Time-Reversal Imaging

The elastic Time-Reversal Imaging (TRI) method utilizes the elastic wave equation to back-propagate recorded seismic data to locate the passive seismic source. The physical principle is that the reconstructed wavefield can focus on the seismic source location automatically at onset time during time-reversal modelling, which is the same with RTM (Reverse Time Migration). Then a proper imaging condition can be applied to highlight the seismic source. The initial imaging condition which we called maximum energy imaging condition is applied to searching the location of the maximum energy during time-reversal modelling and take it as the seismic source location, the corresponding time is origin time. And the interferometric imaging condition is proposed to account for sparse seismic array or unknown velocity model. These two imaging conditions are first proposed in acoustic TRI method, but could be applied to elastic TRI method in principle. To utilize different wave mode information, PS cross correlation imaging condition is proposed. For a moment source, the elastic time-reversal wavefield will recover the radiation pattern at the origin time around the source, which has minimal value at the source location and exhibits a symmetric radiation pattern around the source location. This phenomenon can lead to small values at the source in PS cross correlation image. In this work, we develop a PS interferometric cross correlation imaging condition by combining interferometric imaging condition and PS cross correlation imaging condition, in which the pseudo Wigner distribution is employed to focus the P and S wavefield with symmetric radiation pattern to the source location before calculating PS correlation. We demonstrate the effectiveness of this new method using a simple layer model and a part of complex Marmousi model. The data noises, effect of model's inaccuracy and ability to locate overlapping events are discussed.