Geometric and Dynamic Patterns of the Golmud Segment in the Southern Marginal Fault of the Qaidam Basin

Hao Luo,Yasen Gou,Ji Wang,Hongmei Yu,Peng Shu,Zhanwu Gao

doi:10.3389/feart.2021.636554

Abstract

The southern marginal fault of the Qaidam Basin (SMQBF) is a block-bounding border fault that has played a key role in the structural evolution of the Kunlun Fault. However, its geometric and dynamic deformation patterns since the Late Pleistocene have not been clearly observed. Field investigations, combined with high-resolution imagery and shallow seismic profiles, show that the SMQBF is a thrust fault with a sinistral strike-slip component composed of several secondary faults. Its Late Quaternary deformation pattern is characterized by piggyback thrust propagation, and the frontal fault may not be exposed to the surface. Due to the flexural slip of the hanging strata of the secondary fault, sub-parallel faults with widths of thousands of meters have formed on high terraces; these are important when assessing the seismic hazard of this area. Based on high-resolution topographic data obtained using an unmanned erial vehicle and optically stimulated luminescence chronology, the slip rates of several secondary faults were obtained. The vertical and strike-slip rates of the SMQBF were determined to be 0.96 ± 0.33 mm/a and 2.66 ± 0.50 mm/a, respectively, which may be the minimum rates for the fault. Considering that the SMQBF is composed of several secondary faults, these rates possibly correspond to minimum deformation only. The evident sinistral strike-slip of the SMQBF indicates that although the sinistral slip of the Kunlun Fault system is concentrated in main fault of this system, the branch faults have a significant influence on the lateral extrusion of the Qinghai-Tibet Plateau.

Highlights

The Indian Plate collided with the Eurasian Plate at 55 ± 5 Ma and has since been continuously moving northward (Dupont-Nivet et al, 2010; Hu et al, 2015)
Kunlun and Kunlun Mountain Pass faults are dominantly characterized by sinistral strike-slip, and the slip rate of the middle segment is as high as ∼12 mm/year (Van Der Woerd et al, 1998; Van Der Woerd et al, 2000; Van Der Woerd et al, 2002)
The Kunzhong Fault, which is located between the SMQBF and the Kunlun Fault exhibits evident sinistral strike-slip; a series of gullies are sinistrally displaced by 7–18 m (Wu et al, 1994)

Summary

INTRODUCTION

The Indian Plate collided with the Eurasian Plate at 55 ± 5 Ma and has since been continuously moving northward (Dupont-Nivet et al, 2010; Hu et al, 2015). The southern marginal fault of the Qaidam Basin (SMQBF) has experienced earthquakes with very slow deformation rates and had been assigned a low seismic hazard rating (China earthquake administration, 2015). The slip rate and deformation model of the fault since the Late Pleistocene were determined to facilitate seismic hazard assessment of the southern Qaidam Basin and Golmud City, which constitute an important transportation junction of the Qinghai–Tibet Railway in western Qinghai Province. The SMQBF underwent intense movement in the Early and Middle Quaternary (Engineering Seismology Research Center, China, 2001) It developed a curved anticline with an axial direction that is consistent with the fault strike in Nuomuhong. The fault displaced the bedrock and strata from the Paleocene to the Middle Pleistocene, with a dip angle of 45° (Qinghai Petroleum Administration, 1986)

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