Abstract
<jats:p>Stress changes during hydraulic stimulation affect permeability enhancement and induced seismicity in enhanced geothermal systems, but they are difficult to resolve in space and time. Using 791 focal mechanisms derived from Bayesian inversion of deep-learning-based P and SH polarities and P/S amplitude ratios during the April 2022 Stage 3 stimulation of well 16A(78)-32 at Utah FORGE, we analyze the detailed spatiotemporal evolution of the stress field. We estimate principal stress orientations and the stress shape ratio with iterative linear stress inversion. The reservoir-average stress field is strike-slip, with SHmax oriented ∼ 27◦ from north and stress ratio R ≈ 0.19. The low stress ratio indicates SHmax ≈ SV . Time-window inversions show a modest rotation of SHmax during early injection. Depth-window and cluster-based analyses show that localized normal-faulting stress states are concentrated near the injection interval (2473–2511 m) and are most active during early injection. Three-dimensional coupled hydromechanical simulation provides a framework for examining stress variability and identifying areas where SHmax − SV < 0. These areas overlap with some of the observed normal-faulting events, while mismatches suggest that additional processes and/or unresolved heterogeneity may also</jats:p>