Effect of Errors in the Migration Velocity Model of PS-Waves on Travel Time Accuracy in PSTM in Weak Anisotropic Media

摘要

We investigate the effect of errors in the migration velocity model of PS converted waves on the traveltime calculated in prestack time migration (PSTM) in weak anisotropic media. The PSTM operator contains four parameters, PS-wave velocity, vertical velocity ratio, effect velocity ratio, and anisotropic parameter. We derive four error factors corresponding to the four parameters, respectively. Theoretical and numerical analyses of the error factors show that all the error factors are inversely proportional to the velocity as well as to the travel-time. The error in the PS-wave velocity causes the largest error in the travel-time and the error in the anisotropic parameter causes the smallest error in the travel time. This implies that the effect of four parameters are decoupled. For time processing, we can still estimate PSwave velocity accurately with roughly estimated vertical velocity ratio, effect velocity ratio and anisotropic parameter.