New Insights Into the Heterogeneity of the Lithosphere‐Asthenosphere System Beneath South China From Teleseismic Body‐Wave Attenuation

Teleseismic body‐wave attenuation provides an independent constraint on the architecture of the lithosphere‐asthenosphere system. We obtain the first map of teleseismic attenuation across South China, which correlates well with previous estimates of lithospheric thickness. The weakest attenuation occurs in the Sichuan Basin, where continental lithosphere is thick, and in the adjacent Chuandian region, which we attribute to delaminated lithosphere, or lithosphere strengthened by an ancient plume based on comparison with previous studies. Smaller batches of remnant or delaminated lithosphere may cause local minima along the eastern coast. Pronounced negative anomalies occur in the Hengyang, Jianghan and Nanchang basins, motivating the hypothesis that the basins occur where locally strong blocks within the lithosphere resisted the pervasive deformation of South China. The strongest attenuation occurs in a broad region in the vicinity of the Hainan plume, which is consistent with high temperatures and possibly partial melt in the upper mantle. Plain Language Summary As a classical intracontinental orogen, the detailed deformation of South China is a topic of broad interest. In this study, we present a teleseismic attenuation map based on 9,160 first‐arriving P phases from 82 deep teleseismic events that were recorded by the permanent seismic stations in South China. The attenuation is consistent with the lithospheric thickness revealed by previous results from seismic imaging, flexure modeling, and heat flow. In addition, the low attenuation in the Sichuan basin, Chuandian fragment and other basins, as well as high attenuation in Hainan Island are observed. Several other weaker local maxima require Qp values in the asthenosphere sufficiently low so as to be consistent with upwelling mantle, suggesting that small‐scale convection is pervasive across the region without causing significant volcanism at the surface. Combined with previous studies, the results support the occurrence of lithospheric dismemberment in Eastern China and provide an additional perspective on lithospheric strength and hot spot activity. Key Points The attenuation in South China is obtained from teleseismic body waves Attenuation suggests lithospheric thickness decreases from NW to SE Hainan Island has a high attenuation in the mantle, consistent with a plume feature