Q Least-Squares Reverse Time Migration with Density Disturbance Based on the First-Order Viscoacoustic Quasi-Differential Equations

Abstract

Summary Seismic wave attenuation caused by the subsurface viscoelasicity reduces the quality of migration and the reliability of interpretation. A variety of Q-compensated migration methods are developed based on the second-order viscoacoustic quasi-differential equations. However, these second-order-equation based methods are difficult to handle with density perturbation and surface topography. In addition, the staggered grid scheme, which has an advantage over the collocated grid scheme because of its reduced numerical dispersion and enhanced stability, is unavaiable to implement in these methods. A topography-dependent Q least-squares reverse time migration (Q-LSRTM) based on the first-order viscoacoustic quasi-differential equations is proposed by deriving Q-compensated forward-propagated operators, Q-compensated adjoint operators and Q-attenuated born modeling operators. In addition, the proposed method using curvilinear grids is available even when the attenuating medium has severe surface topography and can conduct Q-compensated migration with density perturbation. Numerical example on a typical model shows that our method improves the imaging quality with iterations and produces better imaging results with clearer structures, higher signal-noise ratio, higher resolution and more balanced amplitude by correcting the energy loss and the phase dispersion caused by the Q attenuation, and suppressing the scattering and diffracted noise caused by the surface topography.