Crustal and Mantle Structure of the Bohai Bay Area Based on Gravity and Magnetic Data

Bohai bay basin is the center area of the destruction of North China Craton (NCC). The deep structure study of the Bohai Sea plays a key role in understanding the scope and dynamic process of the destruction of NCC. In this paper, we studied the crustal structure of the profile from Xincheng, Jinghai, to Bohai Sea along the southeast direction based on the gravity and magnetic data. The initial model was build based on the former studies about the sedimentary structure, deep crustal structure and the onshore-offshore seismic survey in 2010. Combined with the density and magnetic susceptibility parameters in this area, the crustal structure and the physical parameter distribution were determined using 2.5D gravity and magnetic inversion method. The integrated study indicates that the Moho becomes shallower from the land to the sea. The Moho of the Bohai Sea is shallower, and has a local uplift in Shaleitian area with about 2 km uplift. The variation of the Moho is similar with the lithosphere thinning in the eastern NCC. It reflects that lithosphere and deep crustal structure were similarly affected by the destruction of the NCC from Mesozoic. We do the deep uplifting modeling to test the gravity effects from the mantle uplifting. Combined with the analysis of the gravity of the profile, it is less likely to have mantle plume or large mantle uplifting in the Bohai Sea, the local small uplifting of the Moho in Bohai Sea is likely related with a small anomaly body in the upper mantle.