A new crustal thickness model for mainland China derived from EIGEN-6C4 gravity data

摘要

In this study, we present a new crustal thickness model of mainland China created from the inversion of EIGEN-6C4 global gravity model. We took advantage of a high-resolution gravimetric data and the regularized inversion, based on the Gauss-Newton formulation of Bott's equation to resolve the Moho topography. The inversion process uses tesseroids to account for the earth curvature. Moho depth modeling for such a massive landmass cannot ignore the earth's curvature. The Bouguer effect, terrain effect, and gravity effect due to sediments were also corrected and calculated in a spherical approximation. The resulting crustal thickness model was validated with 2992 seismological data points and compared with continental-scale crustal thickness models for mainland China. The final crustal thickness model shows a minimum value of similar to 26 km in Eastern China to a thick crust of over 75 km under the Tibetan Plateau. Nevertheless, the results also show a considerable difference in unconstrained areas of the Tibetan plateau with a crustal thickness of similar to 20 km and similar to 6 km in sedimentary areas. The tectonic terranes show similar depth estimates for all the continental scale models of mainland China, but the lateral variation differs considerably. The results also expose two East-West fold belt trends on the Tibetan Plateau, a 44 km thick crust between Western and Eastern China, and a 37 km NNE trend line, which separates the stable eastern cratonic blocks from the thinned crustal blocks. Overall, our high-resolution model yields an improved representation of crustal features over previously gravity crustal thickness models of mainland China.