Influence factors of converted wave prestack time amplitude-preserving migration by pseudo offset

POM(Pseudo Offset Migration) is a prestack time migration method which is based on Kirchhoff integral.It has the advantages of improving the sharpness of the imaging at common reflection points,and is independ with the velocity model.At the same time,it also has good amplitude preserving ability and relatively low computation expense.Futher more,it can obtain a good imaging under the condition that the lateral velocity has not a large variation.So it is an important method for Converted Wave Prestack time Migration.POM method converts the double square root(DSR) travel time equation of the seismic waves into a single square root hyperbolic equation whose variable is pseudo offset.Since POM doesn' t put the pseudo shot and the pseudo receiver at the same point,the ray path of POM meets the Snell' s Law.And then,the true common reflection point gathers can be extracted.The gathers does not need DMO correction.The process of forming CCSP gathers is equivalent to the prestack time migration process.With the development of the AVO technique,the AmplitudePreserving is more and more important in the process of migration.This paper analyzes the influence of the initial velocity,pseudo offset and migration aperture to the common conversion scatter point(CCSP) gathers.The modeling results of the converted wave POM amplitude-preserving prestack time migration imaging show that to select the appropriate pseudo offset interval and migration aperture is crucial in using pseudo offset to perform prestack time migration.