Multi-component elastic reverse time migration based on the P- and S-wave separated velocity-stress equations

The vector P- and S-seismograms in an elastic common-shot gather generated with a P-wave source in a two-dimensional model using a finite difference solution of the P- and S-wave separated velocity-stress equations can be imaged by two independent ERTMs based on the same equations. The inputs as boundary conditions for reverse-time extrapolation are the pure vector P- and S-waves, respectively. The vector P-wave image components can be obtained by the normalized correlation operation between the vector P-source wavefields and receiver wavefields, which are obtained by extrapolating the vector P-seismograms in reverse-time using the same equations as the forward modeling. The vector S-wave image components can be obtained by a similar method. Compared with the conventional ERTM, this method can minimize the artifacts caused by the crosstalk between different wave modes and can preserve the phase and amplitude attributes of migration images very well. Furthermore, the polarity-reversal of the vector S-wave data can be corrected automatically during the imaging process, so destructive interferences between data from adjacent sources do not exist. Numerical examples with synthetic data have demonstrated the feasibility and effectiveness of this method for complex structures. (C) 2014 Elsevier B.V. All rights reserved.