Dynamic analysis of deformational structures of the Xiannushan fault zone in the three gorges of the Yangtze River

Field investigation and laboratory work reveal that inhomogeneity of the de formation of the Xiannushan fault is mainly characterized by lateral zonati on, longitudinal segmentation and downward stratification. Based on these r esults, a 3-D deformational structure model of the fault was established an d its geometrical and kinematic characteristics in two main deformational s tages i.e. the main Yanshanian and Himalayan were discussed. The directions of principal and the differential stresses in these two stages were determ ined by using conjugate joints, striations of fault planes and microstructu res of the fault zone. The direction of sigma(1) is N-S in direction with d ifferential stresses of 150-250 MPa in the Yanshanian, and N70E with a diff erential stress ranging from 80-120 MPa in the Himalayan.