Detailed Moho geometry beneath southeastern China and its implications on thinning of continental crust

Abstract

We used teleseismic P-wave receiver functions and the H–κ stacking method to obtain crustal thicknesses beneath 121 permanent stations in the Middle-lower Yangtze craton and its adjacent areas, using nearly 700 teleseismic events in 2009 and 2010. We then combined them with results of previous work to map detailed Moho geometry in the region. The results show that in addition to overall thin crust of ∼30km in thickness throughout southeastern China, there are two NS-oriented narrow zones of extensive crustal thinning in the region. The western zone passes through the Xiangzhong Basin, the Jianghan Basin, and the Nanxiang Basin, while the eastern zone follows the Tanlu fault. The two merge in the south, forming a V-shaped thin crust area in southeastern China. We suggest different geodynamic mechanisms of crustal thinning north and south of the 29°N Parallel. Crustal thinning in the northern part was caused by the westward subduction of the Pacific plate and its eastward migration of the trench. Crustal thinning in the southern part is mainly controlled by the interaction between the Philippine and the Eurasia plates. The change of subduction polarity from the northward subduction of the Philippine plate under Eurasia to the eastward high-angle subduction of the Eurasian plate under the Philippine plate in Taiwan is responsible for diverse extensional stress regime in South China. The V-shape crustal thinning zone was formed due to a mantle corner flow in the rear of subducting Eurasia plate, in a form of “hot fingers” growing from the mantle corner flow to cause the Moho uplift in the southern part of the region.