A study of crustal deformation beneath the Qinling Orogenic belt, Central China based on receiver function data

Abstract

A joint shear wave splitting technique based on receiver function data is employed to invert the crustal anisotropy, Moho depth, and Vp/Vs ratio in the Qinling Orogenic belt (QOB). Our findings reveal a relatively low Vp/Vs ratio (∼1.74) and a thin crust in east QOB. This suggests that potential crustal flow from central Tibet may not significantly influence the crustal deformation in east QOB. Our results demonstrate high Vp/Vs ratios (∼1.75–1.88), thick crust (∼44–56 km), and significant crustal anisotropy with a delay time of 0.22–0.86 s in south QOB, Dabashan, and west QOB regions. The fast directions of crustal anisotropy in the south QOB and Dabashan areas are NW-SE, which reflect the orientation of crustal fabrics associated with the collision between the North China Block and the South China Block. However, weak or negligible splitting times are observed beneath the Shennongjia-Huangling (SNHL), Hannan-Micang (HNMC) domes, and Jianghan Basin. The presence of weak crustal anisotropy is likely related to the stable basements beneath two domes, while the negligible splitting time beneath the Jianghan Basin might be attributed to the nearly vertical α-axis of olivines or mica associated with a subvertical mantle flow caused by slab break-off of the subducted Yangtze Block. The underlying magmas have gathered in the lower crust and formed the mafic lower crust, which cause an increase in the crust Vp/Vs ratio and crustal extension.