Three Dimension Construction and Magnetic Fabric Analysis of the Yanjinggou Fault-propagation Fold in Western Sichuan, China

Recently, there is a transition trend of the research on the fault-related fold from 2D to 3D. Based on ARCGIS, DISCOVERY and GOCAD software platform, we built a 3D geological model of the Yanjinggou anticline using 3D seismic data in the area. It was found that Yanjinggou anticline was a typical trishear fault-propagation fold. Because the structural interpretation of the 3D model only is of non-uniqueness and uncertainty due to geometric constraint, the finite strain analysis was also applied in the structural interpretation. 184 oriented samples have been drilled at 18 sampling sites in Yanjinggou, western Sichuan. AMS of these samples disclosed: (1) that most of the magnetic fabrics were the initial deformation fabric; (2) that deformation in the forelimb was relatively stronger than that in the rearlimb; and (3) that the finite strain was strong within the trishear zone of the fault-propagation fold, in accordance with demonstration in the 3D geometric model. The tectonic stress field indicated by the magnetic fabrics suggested a NW-SE compression and shortening, which was consistent with the prediction of the 3D geometric model.