Quantifying the Geometric‐Mechanical Decoupling of Local Stress Fields in Strike‐Slip Faults via Discrete Element Modeling and Response Surface Methodology

Local stress field heterogeneity within fault zones remains a primary bottleneck for accurate seismic hazard assessment. To elucidate the mechanisms by which creeping segment characteristics dictate the local stress evolution, this study constructs a 3D discrete element model under high‐stress boundary conditions equivalent to a 10 km depth. Integrating Plackett–Burman screening with Response Surface Methodology, we quantify the nonlinear interactions between geometric configurations and physico‐mechanical parameters. Rigorously grounded in the statistical self‐similarity of rock fracture, our meter‐scale mechanistic insights provide a scalable framework for understanding crustal‐scale strike‐slip faults. Results demonstrate a significant “geometric‐mechanical decoupling” mechanism: local peak stress is predominantly governed by a geometric filter (connectivity ratio, 45.7% contribution), whereas principal stress deflection is primarily controlled by a physical filter (rock compressive strength, 41.1%). Notably, the stress deflection angle exhibits an upper range of approximately 30° under the investigated conditions, which is mechanically compatible with the favorable orientation for secondary shear activation and marks a transition from predominantly elastic stress rotation toward increasingly localized damage. This decoupling model clarifies the distinct physical origins of stress accumulation and reorientation, providing a quantitative basis for identifying stress‐locked zones and secondary rupture mechanisms.