Fault interaction and active crustal extrusion in the southeastern Tibetan Plateau: Insights from geodynamic modeling

Abstract

• The 3D model is used to investigate the fault interaction and crustal deformation . • Faults in southeastern Tibet are kinematically linked and mechanically coupled. • Fault interaction has affected fault activities and crustal extrusion rates. In the southeastern Tibetan Plateau, the Xianshuihe-Xiaojiang fault system (XXFS) and its neighboring fault systems collectively accommodate the crustal extrusion of the Tibetan Plateau. However, we do not clearly understand how these faults interact with each other and how the fault interaction impacts fault slip rate, strain partitioning and crustal extrusion in this region. Through building a 3D viscoelastoplastic finite element model, we investigate the effects of fault geometry, fault configuration, lithospheric rheology and topographic loading on fault slip rate and crustal deformation. We find that the geometrical irregularity of Anninghe-Zemuhe faults in XXFS (a concave bend) prevents the crustal extrusion of the Chuandian (Sichuan-Yunnan) block, and tends to cause the inception of their subparallel Daliangshan fault on their east. On the other hand, the active Daliangshan fault decreases the slip rates on the Anninghe-Zemuhe faults, causing faster crustal extrusion of the Chuandian block. The active Lijiang-Xiaojinhe fault decreases the slip rates of faults in the south and hence hinders the crustal extrusion of the Chuandian block. Besides, the topographic loading plays an important role in the crustal extrusion of the southeastern Tibetan Plateau, by redistributing regional deformation and fault slip rates. Modeling results demonstrate that all faults in this region are kinematically connected and mechanically coupled: the slip rate change of one fault, both induce strain repartitioning and variations of slip rates on all other faults in such a system. Our research reveals the significant impact of fault interaction on fault activity and crustal extrusion in the southeastern Tibetan Plateau.