An Experimental Study of the Failure Process of En-Echelon Fault Structure Using Digital Speckle Correlation Method

The failure process of en‐echelon fault structure is studied by experiment and the evolution of the deformation field during failure is inspected and analyzed using digital speckle correlation method (DSCM). The fault structure is simulated by a marble plate with 2 parallel slits that were firstly cut and then filled with gypsum. The specimens are loaded on a large double‐axis test machine. The DSCM system captures speckle images continuously during experiment and then processes them to obtain deformation field. The whole failure process of echelon fault structure was revealed by evolution of the deformation field. It is shown that the deformation is firstly localized around the fault and then the echelon area, where the two faults are interactive with each other. The failure also finally evolved in this echelon area. Moreover, the deformation field during loading is statistically studied and a quantitative Cv‐value, which expresses the characteristics of deformation localization, is an indicator for the failure of the echelon fault structure.