The Effects of Fault Geometry and Kinematic Parameters on 3D Fold Morphology: Insights From 3D Geometric Models and Comparison With the Dushanzi Anticline, China

Abstract

Abstract Precise knowledge of the geometry of faults and folds at depth is important for tectonics, economic geology, and seismic hazards. However, the geometry and kinematics of faults and the aspects controlling the coevolution of folds are difficult to constrain without 3D seismic data. We perform a series of 3D forward geometric simulations using a pseudo‐3D trishear fault‐propagation folding algorithm to investigate the effects of six fault geometry and kinematic parameters on the 3D fold morphology. We conclude that the ramp angle and the shortening/fault length ratio are the primary controlling factors of the whole 3D‐fold morphology, and the displacement gradient angle only affects the along‐strike deformation. We then present a quantitative interpretation of the Dushanzi anticline and propose that the anticline formed by trishear fault‐propagation folding with 5.5 km of total shortening. A consistency between the 3D structural and geometric models demonstrates the validity of the structural interpretations, suggesting that the anticline is controlled by a 40‐km‐long fault and has increased in amplitude over time with a shortening rate of ~2 mm/year since the Quaternary. The consistency highlights the spatial relationship between the fault geometry, the along‐strike shortening distribution, and the 3D‐fold morphology. These novel insights from the Dushanzi anticline can be applied to the identification of a structural trap with a volume of 68.6 km 3 .