Abstract: In this paper, we develop a new crustal velocity model in Ningxia region, which is obtained by finite-difference forward modeling and genetic algorithm inversion. Configuring the model into HYP2000 method in MSDP software, we analyzed earthquakes and explosion data from the 3 aspects of epicenter position, depth and residuals since 2008. The results show that epicenters located with new model are closer than older models to faults, and the depths of earthquake swarm located with the new model are also closer to faults. The average depth of explosions is 2.8 km (only a few over 5 km), and the horizontal difference between locating results and explossion sites is 2.4 km, while vertical difference is 2.6 km, which tally with the actual situation (explosions always take place on the ground). Furthermore, we found that earthquake depth is related to velocity structure in Ningxia area, and earthquakes always happened in high-low velocity transition zone.

Key words: Crustal velocity model, HYP2000 method, Earthquake location, Ningxia area