Geometrical imagery and kinematic dissipation of the late Cenozoic active faults in the West Qinling Belt: Implications for the growth of the Tibetan Plateau

Abstract

The West Qinling Belt (WQB) situated in the central China continent, is an enormous structure on the crustal scale, which is not controlled only by the Tethyan tectonic domain but is more complex, involving additional tectonic domains. The composite WQB as the coordinate system, which underwent five major episodes of accretion and collision between discrete continental blocks, has distinct geological and geophysical structure, geomorphology and environment, characterized by complex structures, complex forming processes and mixed materials. Moderate-strong earthquakes occurred frequently in the WQB in recent years, attesting its tectonic activity. Numerous results from the studies related to active fault geological and geodesic observations gave us new insights into present-day crustal deformation characteristics and its dynamic mechanism and helped us in exploring the control effect of active tectonic system on significant earthquake events in the WQB. Two groups of faults striking in different direction (NWW-trending and NEE-trending) within the WQB have played significant roles in the tectonic deformation and the transference slip along the east end of the east Kunlun fault since the Quaternary. Recent results suggest that the < 2 mm/a slip rate at the tip of the east Kunlun fault is absorbed by low slip rate faults, crustal shortening, basin formation, mountain uplift and block rotation in the WQB. Whereas deformation in the shallow brittle crust does not occur on a major fault, deformation of a continuous medium at depth best describes the present-day tectonics of the WQB. Regionally, mantle magmatism, geophysical and geological data show that the actively deforming WQB crust is dominated by main mountain building contraction shortening strain in the upper crust, decoupled plastic deformation in the lower crust and extrusion of the mantle lithosphere below to the high-strain domains in the crust above, and such a transition zone (high and low velocity/resistivity anomalies) is relatively easy to accumulate stress, leading to occurrence of major earthquake in this area.

Keywords

• northeastern margin of the tibetan plateau
• west qinling belt
• intra-continental orogen
• intra-continental deformation
• active fault