The velocity anomaly images in the upper 50 km show certain correlation with the shallow geological features: high velocity zone beneath uplift areas and low velocity zone beneath depressional areas.

• 50 km以上部分的结构与地表的地质构造有较好的对应关系:在燕山隆起区下部表现为高速异常区,而凹陷区下部则呈现低速异常区;