METHODS TO CALCULATE THE FAULT-RELATED STRAIN

This paper presents some methods for calculation of fault strain. The faulting can produce continuous and discontinuous strain. The continuous strain has positive relationship with the ratio of fault displacement vs fault length and with the effective stress on the fault plane. When calculating the discontinuous fault strain, we should consider three factors that affect the establishment of equations: fault geometry, fault rotation, and fault size or fault displacement. There have been three mechanisms of fault rotation: rigid-body, vertical shear, and oblique shear. For these models, the calculation equations are established, respectively. These equations are related to the rotation angle and displacement of fault. For the rigid-body model, the fault has no internal deformation, thus the bed remain its length after rotation. The discontinuous strain due to this mechanism is smallest. The vertical shear produces bed deformation, whereas the horizontal length of bed does not change.The established equation indicates that, using the same data, the discontinuous fault strain is larger than that for the rigid-body model. Similarly, the oblique shear also causes bed deformation, but the horizontal length of bed remains constant. The obtained equation implies that the discontinuous fault strain is larger than that for the vertical shear model in the same condition.