Anisotropic Rayleigh wave tomography revealed lithospheric modification and tectonic deformation mechanisms in Hubei Province, central China

Abstract

The collision of the North China and Yangtze blocks, along with multiple orogenic movements, has caused complex tectonic deformation of the lithosphere in Hubei Province. In order to reveal the stress distribution features and tectonic deformation mechanisms of the regional lithosphere, we inverted an azimuthal anisotropic structural model of the Hubei lithosphere from anisotropic Rayleigh wave tomography with data obtained from 48 broadband seismometers deployed in and around the province. Our model revealed strong lateral variations of azimuthal anisotropy in the crust and upper mantle, providing new seismological evidence for the lithospheric modification of the Yangtze block and the layered deformation of the lithosphere east of the North-South Gravity Lineament. We speculate that the primary dynamic factor causing lithospheric modification in the Yangtze block is related to the rifting events associated with the super-mantle plume, triggered by the deep subduction of the Pacific and Philippine plates. Meanwhile, the rifting event is also the main cause of the lithospheric structural layered deformation east of the North-South Gravity Lineament. The inverted anisotropic model, together with the results of previous geodetic and seismologic studies, revealed the causes and tectonic deformation mechanisms of anisotropy generation in the crust and upper mantle in Hubei Province. Crustal deformation in the Hubei region may be related to the eastward expansion of materials from the Tibetan Plateau and the ultra-high pressure metamorphic zone formed by the subduction and collision of the Yangtze and North China blocks, while upper mantle deformation is associated with subduction and collision of Yangtze and North China blocks, preserved fossil anisotropy from previous orogenic movements, and rifting events tied to the super-mantle plume induced by the deep subduction of the Pacific and Philippine plates. Moreover, we analyzed the regional crust-mantle coupling mechanism and concluded that the crust-mantle in the Dabie orogenic belt is coupled, whereas it is decoupled in other regions.