Stress Distribution and Fracture Development Along the Altyn Tagh Fault:Insights from 3D Discrete Element Modeling

The slip behavior of the Altyn Tagh Fault (ATF) plays a key role in improving our understanding of the tectonic deformation processes shaping the Tibetan Plateau. In this investigation, a three-dimensional (3D) model representing the central segment of the ATF was constructed using discrete element numerical simulations to examine the main damage zones and stress distribution in the Akato Tagh Bend, AKsay Bend, and Xorkoli segments. The simulation results were then cross-referenced with fault orientation measurements from the northern Qaidam Basin and focal mechanism solutions (FMS) to assess their precision and reliability. The results indicate that the stress environment is stable in the linear strike-slip Xorkoli segment, whereas the stress distribution in the Akato Tagh Bend and AKsay Bend segments exhibits significant heterogeneity, with alternating regions of high and low stress. On the concave side of these bends, compressive stress accumulates, fostering the formation of local thrust faults or folds along the fault plane. Conversely, on the convex side, tensile stress dominates, promoting the development of normal faults or extensional fractures. In the restraining bend region, tensile stress remains horizontal, though its orientation shifts considerably as fault displacement increases. The bend segments also show significant variations in shear stress, which can lead to the creation of secondary fault features like Riedel shears. The intensity and distribution of shear stress are influenced by the curvature and bending angle of the fault, with larger bending angles in the Akato Tagh Bend producing more pronounced shear stress concentrations. Fractures are primarily concentrated at the fault tips, along fault intersections, and within the fault plane, with the fault damage zone being notably wider in the Akato Tagh Bend and AKsay Bend segments. As fault displacement increases, the width of the damage zone and fracture density initially increase rapidly before reaching a plateau. Moreover, the primary damage zone develops earlier in the restraining Akato Tagh Bend and AKsay Bend segments compared to the linear strike-slip Xorkoli segment, which absorbs more strain before the principal displacement zone forms. Therefore, the Akato Tagh Bend exhibits the highest fracture intensity, followed by the AKsay Bend and Xorkoli segment. These findings offer significant insights into the slip behavior and stress distribution along the ATF and enhance our understanding of the tectonic processes in the Tibetan Plateau.