The Puguang exploration area in the northeastern Sichuan Basin,China,is characterized by complex surface and subsurface conditions due to the influence of multistage tectonic movements.This dual complexity poses a challenge to precisely characterizing special geobodies like anhydrites in this area,leading to inaccurate velocity field establishment.Consequently,the seismic imaging quality is severely degraded,hindering the fine-scale exploration and production of oil and gas.To enhance velocity modeling accuracy and improve seismic modeling and imaging effects for complex structures,this study investigated the application of a joint velocity modeling method integrating full waveform inversion(FWI) for complex mountainous terrain.A depth-domain velocity modeling workflow based on FWI was developed for the Puguang exploration area.The joint inversion combining tomography and FWI,enhanced by incorporating geological constraints to improve FWI stability,results in a velocity model that effectively matches the subsurface structures.The test using actual data demonstrates that FWI can significantly improve the detail characterization accuracy of velocity models for complex transition zones.This improvement is particularly evident in the enhanced imaging of complex structures in the Dawan and Maoba blocks in the Puguang exploration area.