The Fracture Fabrics And The Deformation In The Thrust Fault Zone

Thrust fault zones, as important structures exit in the earth crust, their kinematics characteristic and the geometric deformation is always a hotspot in geology field. Thrust faulting produced with rocks deformation often lead to a large number of fractures, which recorded the rocks stress strain characteristics and change. The formation of these fractures are most relate to the faults, which are of great significance to the study of fault movement and deformation of rocks.This paper research on"YanJingXi"thrust fault zone in the western margin of Sichuan Basin, carry out a detailed study of fractures near the fault zone from the fracture fabrics, density and deformation characteristics, and do further elaborates the development law of the fractures near the fault zone. Collected image data (photos) in the research area, measured, recorded and plotted the occurrence and shape of fractures, drew up the fracture fabrics of each measuring point as well as each block of the key measuring points, classified the fractures based on the fracture fabrics and analysed the distribution law of them. Taked the measuring points adjoining to the fault as key points, calculated the fracture density of each block of them, analysed the distribution characteristics of the fracture density curves. Analysed the deformation modes of rocks near the thrust fault zone according to the variation characteristics of fractures, dscussed on the calculation method to measure the shear strain by the change of interlaminar shear fractures angle.Early conjugate shear fractures widely developed in the measuring points of the study area. But due to the influence of fracture zone, within a certain range of both sides of the fault zone, the early conjugate shear fractures not development or strong modification and deformation, and produced interlaminar shear fractures and longitudinal tension fractures. Fractures near the thrust fault zone have obvious zonation. Fractures in different zones with different fabrics and density characteristic, the rock rupture and deformation exists three kinds of deformation modes:strong shear deformation, secondary shear deformation and weak shear deformation, these resulted from the stress intensity, lithology and strata thickness and other factors near the thrust fault zone. The changing trend of the variation of relative size of shear strain in rocks is very similar to the density of shear fractures. The stronger interlaminar shear strain the greater the density of interlaminar shear fractures, there is a positive correlation between them. These research methods and results for measures of rock shear strain size have certain reference significance.