Viscoacoustic reverse-time migration imaging based on fractional Laplacian with up-going and down-going wave decomposition
WANG Xipeng1,2,3, ZHANG Qingchen1,2, MAO Weijian1,2
1. Center for Computational and Exploration Geophysics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, Hubei 430077, China; 2. State Key Laboratory of Geodesy and Earth's Dynamics, Wuhan, Hubei 430077, China; 3. University of Chinese Academy of Sciences, Beijing 100049, China
Abstract:The subsurface media typically exhibit viscosity, which causes energy attenuation and(phase) dispersion effects during seismic wave propagation and in turn reduces the illumination energy of migration imaging. The twoway wave equation reverse-time migration with cross-correlation imaging conditions may produce low-frequency noise and false images when there is no highly accurate velocity models or strong velocity gradients. To this end, this paper proposes a viscoacoustic reverse-time migration method based on decoupled fractional Laplacian with up and down-going wave decomposition(Q-compensated reverse-time migration method). The viscoacoustic wave equation based on decoupled fractional Laplacian is employed to separately extrapolate the source wavefield and receiver wavefield and correct the attenuation effects generated by subsurface media during the process. An adaptive stability factor is introduced to handle numerical instability arising from the attenuation compensation of seismic waves. The time-domain analytical wavefield extrapolation method is adopted to separately decompose the propagation directions of the source and receiver wavefields on each time slice. Finally, the cross-correlation imaging condition is utilized for imaging of the down-going source wavefield and up-going receiver wavefield. Numerical tests show that the Q-compensated reverse-time migration method can correct the amplitude attenuation and(phase) dispersion effects caused by the viscosity characteristics of subsurface media. This imaging method significantly reduces the low-frequency noise and false images in traditional reverse-time migration imaging.
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