Quantitative Analysis of Morphotectonic Features of the Longxian-Qishan Fault in the Southwestern Margin of Ordos Block

The Longxian-Qishan fault, located in the joint of the northeast of Tibetan Plateau, Ordos Block and Weihe River Basin, is the forefront to the northeast of the Tibetan Plateau, and also the linking between the Haiyuan-Liupanshan fault and the northern Qinling fault system. In-depth study of its tectonic geomorphic features, tectonic activities and dynamic mechanism is helpful to further understanding the NE extension mechanism and tectonic transformation of NE Tibetan Plateau. Based on 30m resolution ASTER-GDEM data, this article analyzed the structural geomorphologic features and tectonic activities by geomorphologic parameters, and estimated the vertical slip rate according to the empirical formula. The fault can be separated into seven geomorphic segments according to the linear feature of mountain fronts. Analysis of the extracted tectonic geomorphology index of 48 drainage basins and 31 mountain front facets and the estimated uplift rates reveal a general pattern of strong tectonic uplift in the southeast and weak tectonic uplift in the northwest. Combined with the above research results and the fault kinematics characteristics, the dynamic mechanism of tectonic geomorphologic evolution was also discussed. The above research suggests that Longxian-Qishan fault is affected by the northeastern extension of Tibetan Plateau and the northwest section of the fault is dominated by left-lateral strike-slip movement while the southeast is dominated by tectonic uplifting with a northwest tilting direction under the influence of Weibei uplift.