Fault linkage and interaction in active thrust fault systems: examples from the Western Sichuan foreland basin, China

We describe thrust fault segments cases of Qiongxi and Longquan anticlines in western Sichuan foreland basin, China to reveal the fault linkage and interaction processes in active thrust fault system using high-resolution 2D and 3D seismic reflection dataset. Seismic interpretation suggested that the Qiongxi anticline can be divided into three west-dipping, hard-linked thrust fault segments and that it merges downward a regional shallow detachment. Quantitative interpretations of the structural shortening, fault displacement, and fault dip along strike revealed that the lateral linkage of the fault segments limits their development, affecting the along-strike fault displacement distributions. The deficit between shortening and displacement increased with the arising of complex structural processes such as fault surface bifurcation and secondary faulting, demonstrating the effect of the thrust fault segments linkage processes. Structural shortening and fault displacement distributions allow us to identify the two end-member models for the formation of this segmented fault array effectively: (1) isolated fault model and (2) coherent fault model. These models are used to interpret the fault displacement distribution and kinematic relationships of the segmented, thrust fault-related folds. Our measurements revealed the process of fault surface bifurcation from the main thrust ramp and its influence on the internal strain and slip distribution. Moreover, we found that the spatial correlation between the lateral linkage site of the thrust segments and the deflection of the main channel of a piedmont alluvial fan reflect the impacts of the subsurface structural linkage on the evolution of the alluvial fan. This work provides an example of the lateral propagation and interaction of a thrust fault array, which could also provide insight into the fault linkage and tectonic geomorphology in other contractional tectonic settings.