Numerical Simulation of Deformation and Stress Processes in Fault-Bend Folding: Quantitative Constraints Based on Elastoplastic Parameter Control

Objective Fault-bend folds, characteristic structures in fold-and-thrust belts, act as key kinematic units for analyzing compressional deformation and form structural traps at flat–ramp transitions, making them critical targets in foreland basin hydrocarbon exploration.Methods Using Suppe’s theoretical model and finite element simulations, we developed a geomechanical model with realistic rock properties. Boundary conditions for fold formation were defined, and stress-strain patterns during evolution were analyzed. The Mohr–Coulomb model was applied to assess six parameters—density (ρ), Young’s modulus (E), Poisson’s ratio (υ), internal friction angle (ϕ), cohesion (c), and dilation angle (ψ)—for identifying dominant controls.Results Open boundaries enable fault-bend fold development consistent with classical models, whereas fixed boundaries cause marked forelimb tilting and non-classical deformation. Stress-strain partitioning is distinct: fold limbs and the upper ramp experience compression; the core and upper flat undergo extension. Both axial surfaces show upward-decreasing stress concentrations and plastic strain. The lower axial surface builds the backlimb and initiates shear fracturing; the upper axial surface shapes the anticlinal core and forelimb under tension, developing potential fracture systems. Cohesion (c) and internal friction angle (ϕ) are key, governing fold wavelength and forelimb steepness, respectively, with nonlinear threshold behaviors. Young’s modulus and dilation angle have localized, minor influence; density and Poisson’s ratio show negligible effects.Conclusion Fault-bend folding evolves as a progressive deformation where strata adjust to pre-existing fault geometry under compression, forming a kinematic sequence from initial slip and backlimb growth, through fold nucleation and propagation, to final stabilization with complex derived structures. Cohesion and internal friction angle are the decisive controlling parameters.Significance This numerical analysis clarifies the development mechanisms, stress-strain organization, and controlling factors of fault-bend folds, deepening the theoretical understanding of compressional tectonic deformation.