The North China region is roughly divided by the Tai Hang Mountains into two geological blocks: Eerduosi block in the west and the Hehuai block in the east. A least squares technique is applied to extract the pure path group velocities in the two blocks. From mixed path Rayleigh wave group velocities of fundamantal model. Numerical inversion from the pure path group velocity dispersion is made to study the layered structures of the crust and upper mantle in the two blocks. The results of this work show considerable differences between the two blocks in surface wave dispersion and velocity structures of the crust and upper mantle. Hehuai block has a smaller crustal thickness and a mean velocity of approximately 0.13 km/s, smaller than that in Eerduosi block. And a low velocity zone seems appear at a depth of about 20 km. However Eerduosi block has a layered structure with gradually increasing velocities with depth. Low velocity zone has not been found in the crust. Both of the blocks have a relatively low velocity at the top of the upper mantle, and a similar depth of low velocity zone in the mantle. Eerduosi block has a thicker low velocity zone in the upper mantle, while its velocity is 0.3 km/s smaller than Hehuai block.
