Abstract:Based on seismic data waveform recorded by Inner Mongolia Seismic Network from 2010 to 2020, we select 3 010 Pg waves and 3 410 Sg waves of 391 earthquakes from 24 fixed stations. Using double-difference tomography, we inverse the three-dimensional velocity structures of Pg- and Sg-wave in the crust on the northern margin of the Ordos block, and relocate all earthquakes in this area. The results show that at 5-15 km depth, there is a large continuous high-speed body in the eastern study area, while the southwest shows the distribution characteristics of relatively low speed. Most earthquakes are concentrated in the transition area between high and low speed areas, which also reflects the vulnerability of crustal media in the study area. At 20-30 km depth, the high-speed area spreads westward with the increase of depth. It is connected to the high-speed area of Hubao basin, indicating that a tectonic body crosses the crust of Hubao basin.