In this paper, the depth of the Moho surface in the South China Sea is investigated by the gravity inversion method under the spatial-domain spherical coordinate system based on the global gravity field model WGM2012. The gravity data are corrected for the lithospheric thermal gravity anomaly due to the large negative residual thermal anomaly caused by lithospheric extension in the ocean and continental margins. The calculation results show that the thermal anomaly is mainly concentrated near the residual oceanic ridges in the South China Sea and that the density anomalies caused by the anomaly show a “fusiform” variation with depth; i.e., the anomaly is larger in the middle of the lithosphere and smaller at the top and bottom. The Moho inversion results indicate that the depth of the Moho surface in the South China Sea ranges from 7 to 32 km with an overall northeastward wedge-shaped distribution and is characterized by a shallow basin and a deep perimeter. In addition, a depression of the Moho surface remains under the remnant oceanic ridges, with the depth increasing by 2–5 km, and the depth of the Moho surface on both sides of the basin changes rapidly. Further, we determined the location of the OCT in the South China Sea based on the Moho depth mapped by gravity inversion and combined it with the results of seismic reflection profiles and other relevant geophysical data; its width is approximately 200 km in the east and 70 km in the west.

本文基于全球重力场模型WGM2012，在空间域球面坐标系下，采用重力反演方法研究南海莫霍面深度。由于岩石圈在海洋和大陆边缘的伸展引起了较大的负残余热异常，因此对重力数据进行了岩石圈热重力异常校正。计算结果表明，热异常主要集中在南海残余洋脊附近，由异常引起的密度异常随深度呈“梭形”变化；即，异常在岩石圈中部较大，在顶部和底部较小。莫霍面反演结果表明，南海莫霍面深度为7～32 km，整体呈东北向楔形分布，具有盆地浅、周界深的特点。此外，残存洋脊下方还存在莫霍面凹陷，深度增加2～5km，盆地两侧莫霍面深度变化较快。此外，我们根据重力反演绘制的莫霍面深度，并结合地震反射剖面和其他相关地球物理数据的结果，确定了OCT在南海的位置；东宽约200公里，西宽约70公里。残存洋脊下方仍存在莫霍面凹陷，深度增加2～5km，盆地两侧莫霍面深度变化较快。此外，我们根据重力反演绘制的莫霍面深度，并结合地震反射剖面和其他相关地球物理数据的结果，确定了南海华侨城的位置；其宽度东约200公里，西约70公里。残存洋脊下方仍存在莫霍面凹陷，深度增加2～5km，盆地两侧莫霍面深度变化较快。此外，我们根据重力反演绘制的莫霍面深度，并结合地震反射剖面和其他相关地球物理数据的结果，确定了南海华侨城的位置；其宽度东约200公里，西约70公里。我们根据重力反演绘制的莫霍面深度，并结合地震反射剖面和其他相关地球物理数据的结果，确定了南海华侨城的位置；东宽约200公里，西宽约70公里。我们根据重力反演绘制的莫霍面深度，并结合地震反射剖面和其他相关地球物理数据的结果，确定了南海华侨城的位置；东宽约200公里，西宽约70公里。