Effective elastic thickness of the lithosphere in the East and South China Seas and adjacent area obtained using the convolution method

The effective elastic thickness (Te) of the lithosphere, which reflects lithospheric strength, is a useful parameter in the investigation of the characteristics of the oceanic lithosphere. Instead of the conventional spectral method, we used a space-domain convolution method to estimate Te, which involves the convolution of the crustal load with a set of point-loaded response functions in order to get a set of model flexures. The best Te estimate is obtained from the best agreement between the model flexures and the observed flexure derived from the inversion of the gravity data. Compared with the spectral method, this method eliminates the instability problem when the topography is small and increases the spatial resolution of Te. Based on this convolution method, for the first time, we determined Te for the lithosphere in the East and South China Seas and the adjacent area. The result shows that the Bohai Sea, the northern part of the Yellow Sea, the northwestern part of the East China Sea, and the Yinggehai Basin have the strongest lithosphere with a Te reaching 30 km. The central part of the South China Sea and the Okinawa Trough Basin have the weakest lithosphere with a Te of less than 6 km. In addition, we investigate the relationship between Te and the distribution of the crustal load and the relationship between Te and the undulations of the Crust Mantle Interface (CMI). We conclude that the lithospheric strength, Te, decreases with an increase in the sufficient old load. Meanwhile, a positive correlation is found between Te and the CMI. When the CMI becomes deeper or shallower, the corresponding Te becomes larger or smaller, respectively.