Inversion of earthquake and explosion data for 3-Dvelocity structure in Ningxia and adjacent region

We applied the finite difference and LSQR algorithm inversion in Ningxia and adjacent region .Using 2003-2009 7 years 426 earthquakes and 52 exploions Pg and Pn first arrival data，Excluding discrete large data remain 2788 records ,we obtained distribution of the image plane at different depths and different positions of the depth direction, velocity profile images. Combined with geological data and previous studies draw conclusions as follow: 0-5km depth average velocity 5.1 km/s, 5-25km depth average velocity 5.9 km/s, 25-35km depth average velocity 6.4 km/s; In shallow low-speed is distributed in Yinchuan graben basin, and Qingshui river basin in Zhongwei and High is distributed in Helan mountain area. In the deep high-speed is distributed in Zhongwei-Tongxin fault zone, Low is mainly distributed in the yinchuan graben and west parts, guyuan qingshui river fault zone.This conclusion is basically consistent with previous studies.