Cenozoic Evolution of the Bohai Bay Basin: Constraints From Seismic Radial Anisotropy

Abstract

We obtain three-dimensional models of crustal shear-wave velocity and radial anisotropy in the Bohai Bay basin (BBB), revealing distinct radial anisotropy patterns. The western region of the basin exhibits pronounced positive crustal radial anisotropies, attributed to upper mantle convection driven by the subduction of the Pacific plate during the early Tertiary. Conversely, the eastern region of the basin demonstrates weak to negative radial anisotropies, indicating a compression shear rupture system influenced by the far-field India-Eurasian collision during the Neogene-Quaternary. These differences suggest that the formation of the BBB is associated with the dynamic transition from Pacific subduction to India-Eurasian collision during the Cenozoic. Moreover, the Luxi uplift, with its stable upper-middle crustal structures, acts as a barrier hindering the eastward extension of the BBB.