中文摘要：

南海处于印度—澳大利亚、欧亚和太平洋三大板块汇聚中心,地理位置独特,地质作用复杂,经历了拉张、张裂到海底扩张的演化过程,是水平拉张和地幔上涌共同作用下的被动扩张结构。以南海中央海盆的地质构造为背景建立二维有限元模型,对具有先存薄弱带情况下岩石圈在水平拉张力和上涌力共同作用下的减薄扩张情况进行动力学模拟。计算结果表明：（1）岩石圈在受到拉张作用时,薄弱带和断层的存在会使该区域发生应力集中,优先减薄破坏;（2）岩石圈在单纯的拉张力条件下很难发生破坏,如果同时施加一个较小地幔上涌力反而能引起较大的变形,说明地幔上涌力在海盆扩张中起着重要的作用;（3）由于下地壳的流变性,下地壳比上地壳发生了更大程度的减薄,而且下地壳的流变特性比薄弱带的存在更有助于海盆的扩张。

英文摘要：

The South China Sea is located at the juncture of the Eurasian,Indian-Australian and Pacific plates and complicated in tectonic location and evolution.It has experienced a process from rifting of a passive continent to seafloor spreading,under the affection of both tectonic extrusion and asthenosphere upwelling.Based on the tectonic and dynamic background of South China Sea,a 2Dfinite element dynamic model with a pre-existing weak zone was prepared to explore the behaviors of the two dynamic forces.The simulation results indicate：（1）The lithosphere where faults or weak zones occur is easier to have stress concentration and crust thinning;（2）The asthenosphere upwelling seems play a more important role in the opening as the tectonic extrusion can hardly cause lithosphere＇s damage,;（3）The rheological properties may have greater contribution to the opening of South China Sea comparing to the existence of weak zone.The rheological properties of the lower crust may cause a greater crust thinning comparing to the upper crust.