The line has twice laid out to sound the crustal velocity structure in Huixian-Lixian region by means of industrial blasts of Changba Lead-Zinc Mine in 1984 and 1985, especially, the explosion of 500 ton charge on Dec. 30, 1985 supports us to interprete a large scope crustal velocity structure. The parts of DSS data obtained by DSS Cooperation Group, SSB, in 1986 were supplemented.
The velocity structure in Tianshui-Lixian region are following:
1.The average thickness of sedimentary layer is about 2.5km, average velocity is 4km/s (P-wave).
2.The average thickness of crust is 43.6km, average velocity is 6.2km/s.
3.There are five layers from surface to Moho. There is a low-velocity layer in depth 24-29 km. The shape of base is rising and falling.A fault in Lixian was found.
4.The joint inversion of P-wave and S-wave was put forward, and P-wave velocity structure and S-wave velocity structure were obtained, The average velocity ratio of crust is 1,732,