In order to obtain the migration imaging results with clear physical meaning and geological interpretation,the current elastic reverse time migration methods require P/S waves decomposition to the extrapolated elastic wavefields in the migration process to eliminate the cross-talk artifacts generated by physically mismatched wave modes in the migration imaging results.Given a smooth model of subsurface media with accurate kinematic characteristics of seismic waves,this paper first proposes a general forward representation for migration as a linear inverse problem of seismic data.Then,by using the isotropic elastic wave equation,the P/S wave decoupled elastic wave equations suitable for the smooth model of elastic media are derived,namely a P wave elastic wave equation and a S wave elastic wave equation.Finally,a new method and new realization for the isotropic elastic reverse time migration are proposed.For the reverse time migration of isotropic elastic wave seismic data excited by the pure P(or S)wave source,a new method is proposed,which does not need the P/S waves decomposition to the extrapolated elastic wavefields and does not appear cross-talk artifacts in the migration imaging results.For the reverse time migration of isotropic elastic wave seismic data excited by P/S waves composite source,a new realization is put forward that even if the P/S waves decomposition is used to the extrapolated elastic wavefields,the cross-talk artifacts still appear in the migration imaging results.
Elastic waveSmooth migration modelReverse time migrationWithout P/S waves decompositionCross-talk artifacts
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万方数据
