New understanding of Anderson fault formation model based on butterfly plastic zone theory

Abstract

Anderson fault model is based on the Mohr-Coulomb criterion, a model to judge the occurrence of fault formation considering the value and direction of in situ stress. The purposes are to explore the similarities, differences, and applicability between the Anderson model and butterfly plastic zone theory in fault generation and reveal the characteristics of fault formation. First, the limitations of the Anderson fault model when applying to fault formation are emphasized. Second, the fundamental principles of butterfly plastic zone theory are introduced, and the mechanical conditions for the normal faults, reverse faults, and strike-slip faults are given. Finally, the three types of faults’ formation characteristics are reproduced through numerical simulation, and the Anderson model and butterfly plastic zone theory are compared and analyzed. Results demonstrate that the fault formation is affected by the direction and magnitude of the in situ stress. The relationship between the fault and the direction of the in-situ stress based on the model is consistent with the theoretical analysis. Compared with the Anderson model, the butterfly plastic zone theory can determine the precise fault locations and obtain the evolution process of reverse faults, normal faults, and strike-slip faults. The Anderson model is challenging to determine the precise fault locations and cannot display its formation process. A macroscopic judgment can find that butterfly plastic zone theory is more precise in determining fault formation.