Features of Fracture Formation in Rock Samples under Comprehensive Compression Using Acoustic Emission

Riedel shears, formed under the action of shear stresses in rocks, are an important element in studying the nature of tectonic deformations. This work investigates their formation using acoustic emission (AE) during triaxial compression experiments. We identify four fracture stages: Stage 1: Dispersed microcracks at 40–80% peak stress. Stage 2: Localized macrofracture nucleation at 0.99σ (tensile strength), with AE activity surge (300–500% increase). Stage 3: Shear deformation along faults. Analyzing the mechanisms of formation of such fracture systems allows identifying patterns of rock failures, which in turn enables predicting the nature of geodynamic processes. This study examines the relationship between local geomechanical processes of Riedel shear formation and global tectonic faults. To address this issue, theoretical and experimental modeling of stress distribution in rock samples under triaxial compression was conducted, along with the analysis of geophysical data confirming the patterns of formation of en echelon fracture systems in natural conditions. As a result of the study, the features of Riedel shear development in idealized (modeled) and real geological environments were determined, and key factors indicating the connection between fracturing and shear deformation zones were identified. The obtained results can be used for interpreting tectonic structures and predicting geomechanical events. A new approach to the interpretation of acoustic emission for predicting shear deformations on the scale of a rock massif has been developed. A novel AE interpretation methodology links hypocenter concentration to shear zones, validated against the 2020 Bystrinskoe earthquake precursors. Results enable predicting geomechanical events and hydrocarbon migration paths.