Seismic Imaging of Lithosphere Structure and Upper Mantle Deformation Beneath East-Central China and Their Tectonic Implications

We conduct a nonlinear joint inversion of receiver functions and surface waves to obtain the lithosphere structure in east-central China. We also use SKS splitting measurements to evaluate upper mantle deformation. The velocity model reveals that, to the east of the North-South Gravity Lineament, the crust and lithosphere are significantly thinned. Three extensive crustal/lithospheric thinning subregions are identified. This indicates that the lithospheric modification in east-central China is nonuniform due to heterogeneity of lithospheric strength. Extensive crustal and lithospheric thinning probably occurs in some weak zones such as basin-range junction belts and large faults. The structure beneath the Dabie orogenic belt is complex due to the collision between the North and South China Blocks during the Late Paleozoic-Triassic. The Dabie orogenic belt is delineated by a thick crust with a midcrust low-velocity zone and a two-directional convergence in the lithospheric scale. The crust and uppermost mantle across the Tanlu fault exhibit a strong seismic velocity contrast, which suggests deep penetration of this lithospheric-scale fault. Most of our splitting measurements show nearly E-W trending fast polarization. The similar present-day lithosphere structure and upper mantle deformation may imply that the eastern North China Craton and South China Block have been dominated by a common dynamic process since the Late Mesozoic. The westward subduction of the Philippine plate and the long-range effects of the collision between the Indian and Eurasia plates during the Cenozoic may have also contributed to the present velocity structure and stress field of eastern China.