Multicomponent joint reverse time migration based on first order velocity-dilatation-rotation equations

Elastic reverse time migration (RTM) is an important technology in multi-component seismic exploration. In order to suppress noise in RTM and correct polarization of S-wave,the propagation directions of P-wave and S-wave have to be calculated accurately. The propagation direction of seismic wave is generally indicated by Poynting vector. The conventional first-order velocity-stress equations could only calculate a Poynting vector which indicates the propa- gation direction of the mixed wavefield rather than that of the P-or S-wavefield. Therefore,it is unable to accurately suppress noise or correct S-wave polarity by using the conventional Poynting vector. Theoretically,the first-order veloc- ity-dilatation-rotation equations could calculate Poynting vectors of pure P-and S-wavefield,which indicate the propa- gation directions of P-and S-wave,respectively. Therefore,the problems in the conventional method could be avoided by using the Poynting vectors calculated by the first-order velocity-dilatation-rotation equations. This paper focuses on the elastic RTM which is based on the first order velocity-dilatation-rotation equations. Firstly,the authors derived a re- verse-time propagation scheme in staggered-grid with 2-order time difference accuracy and 2 N-order space difference accuracy. The authors also derived the stability condition of the scheme. Secondly,the authors calculated the P-and S- wave Poynting vectors to indicate the propagation directions of pure P-and S-wavefield,respectively. Then,the elastic RTM could be implemented by utilizing a cross-correlation imaging condition in the wavefield which is separated by propagation directions. The numerical tests show the elastic RTM based on the first-order velocity-dilatation-rotation e- quations can accurately correct S-wave polarization. In addition,the migrated sections obtained by this method could suppress noise better than the conventional method which is based on the first-order velocity-stress equations.