• Fracture mode evolution correlates with damage level, with shear microcrack propagation primarily governing macroscopic failure in granite.
• A novel method estimates characteristic stresses (crack closure, initiation, damage) by mapping key points on the shear crack proportion curve from AE data.
• The proposed method is validated against the crack volumetric strain method and shows lower sensitivity to AE parameter variations than conventional AE parameters.
• The fracture mode proportion directly reflects microcrack evolution, enhancing interpretability and offering a new perspective for AE-based stress threshold determination.