Abstract: The conventional inversion of anisotropic media is often constrained by assumptions of narrow-angle incidence and weak changes in stratigraphic properties.Moreover,the prediction of rock elastic parameters typically involves linear inversion and indirect fitting,leading to less accurate and reliable inversion results of petrophysical parameters for anisotropic formations.Hence,this study derived the petrophysical models of Young's modulus,Poisson's ratio,and fracture parameters for vertical transverse isotropy(VTI) media.Based on the precise VTI reflection coefficient equation,this study proposed a Bayesian anisotropic nonlinear direct inversion method,constrained by the L₁ norm,to predict the brittleness and fracture parameters of shale gas reservoirs through direct inversion.The proposed method yielded satisfactory application results in a study area of shale gas in Southwest China,offering a novel technique for characterizing shale gas reservoirs.