Abstract:

In view of the impact of  velocity model smoothing on wave traveltime, ray path and the amplitude information, we analyzed the theoretical basis of velocity model smoothing from prerequisite establishment of ray tracing equations, the ray theory of high-frequency approximation and Fresnel zone. Ray paths calculation before and after velocity smoothing for a same model showed that the smoothing of model can effectively improve the coverage of ray tracing without additional initial angle. Ray paths calculation and error analysis of before and after velocity smoothing for different  model showed that selecting a reasonable number of smoothing under the premise of ensuring the viability of ray tracing and coverage, travel time can minimize errors(50 times smoothing in horizontal and vertical, the maximum relative error less than 5% on marmousi model and 50 times smoothing in vertical, the maximum relative error less than 1% on undulating layered model at the same abscissa of all points in z direction) without affecting the quality of migration.

Key words: velocity model, smoothing, smoothing times, error analysis