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利用中国地震台网和ISC台站记录的P波到时数据,采用球坐标系有限差分地震层析成像方法反演了南海东北部及其邻近地区壳幔三维P波速度结构,并分析了不同地质单元的构造差异及其深部特征。结果表明:南海东北部表现出陆架地区的岩石层特性,属于华南大陆向海区的延伸,岩石层厚度较大,现今不存在大规模的地幔热流活动,推测大陆边缘张裂作用仅限于地壳内部而没有延伸进入上地幔,具有非火山型大陆边缘的深部特点。中央海盆附近上地幔P波速度明显降低,与海盆下方地幔热流活动密切相关。不同的速度异常特征表明:华南大陆暨台湾地区属于欧亚大陆的正常地壳或是与菲律宾海板块相互作用产生的增厚型地壳,冲绳海槽则是弧后扩张产生的减薄型地壳。滨海断裂带作为华南大陆高速异常和南海北部高速异常的分界,代表了一定地质时期华南地块和南海地块的拼合边界。断裂附近的上地幔低速异常揭示了闽粤沿海岩浆作用的深层动力机制。吕宋岛弧、马尼拉海沟、东吕宋海槽的速度异常与其所处的特殊构造位置有密切的关系,清晰地反映出岛弧俯冲带的地壳结构差异;台湾南部至吕宋岛弧的上地幔低速异常揭示了两个重要火山链的深部构造特征,北吕宋海脊下方100km深度的条带状高速异常有可能代表了俯冲下沉的岩石层板片。
Based on the P-wave arrival data recorded by China Seismological Network and ISC station, the three-dimensional P-wave velocity structure of the crust and mantle in the northeastern South China Sea and its adjacent areas was retrieved by the finite difference seismic tomography of the spherical coordinate system. Structural Differences of Geological Units and Their Deep Features. The results show that the lithospheric characteristics of the continental shelf in the northeastern South China Sea belong to the extension of the South China Sea to the sea area, and the lithosphere thickness is relatively large. There is no large-scale heat flux in the mantle nowadays. It is speculated that the continental margin is limited to the interior of the crust Did not extend into the upper mantle, with deep features of non-volcanic continental margins. The P-wave velocity of the upper mantle near the central basin is obviously lower, which is closely related to the heat flux in the lower mantle beneath the basin. Different velocity anomalies indicate that the South China and Taiwan belonged to the normal crust of Eurasia or the thickening crust caused by the interaction with the Philippine Sea plate. The Okinawa Trough is a thinned crust resulting from backarc expansion. Binhai fault zone, as the boundary between the high-speed anomalies in the South China continent and the high-speed anomalies in the northern South China Sea, represents the flattened boundary of the South China Block and the South China Sea Block in a certain geological period. The low-velocity anomaly of the upper mantle near the fault revealed the underlying dynamical mechanism of magmatism along the coast of Fujian and Guangdong. The velocity anomalies of the Luzon arc, the Manila trench, and the East Luzonong trough are closely related to the special tectonic positions in which they are located, and clearly reflect the crustal structural differences of the island arc subduction zone. From the southern part of Taiwan to the arc of the Luzon Island The low mantle velocity anomalies revealed deep tectonic features of two important volcanic chains. The high velocity anomalies of 100 km below the Northern Luzon ridge may represent subducted lithospheric plates.