Variations of crustal thickness and average Vp/Vs ratio beneath the Shanxi Rift, North China, from receiver functions

Yifang Chen,Shuncheng Li,Xuzhang Shen,Xuzhou Liu,Zhanyang Yu,Jiuhui Chen

doi:10.1186/s40623-021-01528-8

Yifang Chen, Shuncheng Li + Show 4 more

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https://doi.org/10.1186/s40623-021-01528-8

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Abstract

The Shanxi Rift located in the central part of the North China Craton (NCC) as a boundary between the Ordos block and the Huabei basin. The Shanxi graben system is a Cenozoic rift and originated from back-arc spreading related to westward subduction of the western Pacific and far field effects caused by northward subduction of the Indian plate. It has also had strong earthquake activity in China since the Quaternary. To investigate the tectonic evolution and tectonic setting of strong earthquakes in the Shanxi Rift, we apply the receiver function H-kappa stacking method to determine the crustal thickness and average Vp/Vs ratio in the area. The results show that the thickness of the crust increases from approximately 30 km in the Huabei basin to approximately 47 km in the Yinshan Mountains with a close correlation between the Moho depth and topography. The Yuncheng, Linfen and Taiyuan grabens have varying degrees of crustal thinning. The crustal average Vp/Vs ratio in the Shanxi Rift has significant heterogeneity; the high Vp/Vs ratio (~ 1.85) are found in the Datong and Yuncheng grabens, and Vp/Vs ratio of the Taiyuan and Linfen grabens is approximately 1.75 which close to the global average value ~ 1.782. Combining the observations in this study with previous research, we suggest that the grabens in the Shanxi Rift experienced extensional deformation from south to north and that the possibility of strong earthquakes in the central part of the Shanxi seismic belt is greater than that on the northern and southern sides.

Highlights

The Shanxi Rift is a famous terrestrial rift system and is located in the Trans-North China Orogen (TNCO)
According to the tests we found that the presence of the sedimentary layer with thicker thickness or lager Vp/Vs ratio can produce larger reverberations that strongly interfere with signals of Moho and multiples in RFs and make the H-κ stacking unapplicable (Additional file 1: Figure S5b– c)
In this study, we obtain the crustal thickness and average Vp/Vs ratio of 217 seismic stations based on the receiver function H-κ stacking technique by correcting for the time delay from the loose sedimentary layers

Summary

Introduction

The Shanxi Rift is a famous terrestrial rift system and is located in the Trans-North China Orogen (TNCO). The TNCO was assembled ∼1.85 Ga ago (Zhao et al 2001) and is bounded by the Ordos block in the western North China Craton (NCC) to the west and by the Huabei basin in the eastern NCC to the east. The. Huabei basin, as part of the eastern North China Craton, has undergone intensive lithospheric extension and destruction, and offset rift basins have formed, which are induced by the westward subduction of the Pacific plate and the India–Asia collision (Northrup et al 1995; Tian et al 1992; Liu et al 2007; Chen et al 2009; Zhu et al 2012). The Shanxi Rift, as a transition zone between the Ordos block and Huabei basin, is adjacent to two units with distinct tectonic patterns and is located in a complex tectonic environment.

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