Abstract：The assumption that there is no lateral velocity variation in a stratum is usually made in velocity analysis. However, this assumption does not coincide with real sit- nations at all. The time-distance curves of several shallow lateral velocity variation models are estimated by using ray tracing method. Velocity analysis result shows that shallow lateral velocity variation causes noticeable influence upon deep velocity analysis result, which thus brings an effect being absolutely different from that in laterally uniform medium. It can be seen from this that the effect must be considered in velocity model construction using velocity analysis result.
