摘要
///The authors applied the finite difference and LSQR inversion algorithm to the seismic data in Ningxia and adjacent region. The authors collected Pg and Pn first arrival data from 426 earthquakes and 52 explosions occurred during the 7 years of 2003~2009. By referring relevant geological materials and some previous studies, the authors drawn the following conclusion:the average P-wave velocity for the depth range of 0~5 km is 5.1 km/s, the average velocity for 5~25 km is 5.9 km/s, while that for 25~35 km reaches to 6.4 km/s. In the shallow part the low velocity zones are mainly in Yinchuan graben basin and Qingshui river basin in Zhongwei county, while a major high velocity zone locates in Helan mountain area. In the deep crust a high velocity zone is seen along the Zhongwei-Tongxin fault zone, while low velocity zone lies mainly in the Yinchuan graben and its west, and in Guyuan Qingshui river fault zone. This conclusion is basically consistent with the result of previous studies.